A popular space-saving design for cornhole boards, nesting boards, are made by building one standard board and one board with a recessed frame so that the frames fit into one another. To build these, you will need:

Materials

4 96" 2x4's
1 96" 2x3
6 3 1/2" long 5/16 diameter carriage bolts
2 5/16 diameter nuts
2 5/16 diameter washers
4 5/16 diameter wingnuts
16 2-1/2 inch coarse drywall screws
2 2'x4' pieces of half inch plywood (one sheet of plywood will yield four of these, they can be cut to size in the store where you buy them)
Primer
Paint
Water based polyurethane
Putty
Wood Glue
1-1/2" brads
Chest pull handle
2" webbing
Sew-on velcro

Tools

Chop saw or circular saw
Drill
Hammer
Air compressor
Air powered brad nailer
5/16 drill bit
3/8 drill bit
3/32 drill bit
Countersink bit
6 inch hole saw
250 grit sandpaper/sanding block
putty knife
Paintbrushes
Pencil
Awl
Tape ruler
5/8" paddle bit

This Instructable expands on my previous Instructable, How to make Cornhole Boards: https://www.instructables.com/id/How-to-make-Cornho...

Follow that Instructable through and stop after step 7, so that you have one standard board built.

You can expand upon this design and add wheels as well! This process is detailed in my "How to make Rolling Cornhole Boards" Instructable here: https://m.instructables.com/id/How-to-Make-Rolling-Cornhole-Boards/

Step 1: Making the Nesting Sides

Lay the standard size board flat on the ground with its frame facing upward. Measure the interior of the frame along the long sides. Measure both sides in case the standard board is not perfectly square. Subtract 1/4" from these measurements and cut 2x4's to that length. Set these cut 2x4's inside of the standard frame to verify fitment.

On one end of each piece, measure 4-1/2 inches from the end of the board and make a mark. Measure 1-3/4 inches from the edge of the board to the mark you just made, making a second mark. At the intersection of the marks, take your awl and make a small indentation in the wood. Next, using a drill or drill press and a 5/16 drill bit, drill through the indentation. These holes will be used to hold on the legs.

Use a 5/8" paddle bit, countersink each of the leg holes about 1/8" so that the head of the carriage bolt will be flush with the side when installed.

Step 2: Making the Nesting Ends

Place the sides back into the frame. Measure between the nesting sides on the top and bottom of the board in case the standard board is not square. Subtract 1/4" from these measurements and cut 2x4's to that length. Set these cut 2x4's inside of the standard frame to verify fitment. The boards should not fit snugly into the frame. If they are snug, trim the boards, or they will not want to nest later!

Step 3: Pre-drilling

Take the two side 2x4's. Using scrap wood, elevate them so that you can drill through them without hitting the ground. As shown in the first picture, the boards are laying with their 4 inch sides up. Using your 3/32 drill bit, drill two holes into the side boards 3/4 of an inch from the ends. Do this on both ends of the side boards.

Use your countersink bit on each of the eight pre-drilled holes so that the head of the screws will be below the surface of the wood.

Step 4: Making the Nesting Frame

Now all of the pieces are ready! Lay all of the pieces down in the shape of the frame. Put wood glue on the ends of the end boards. Make certain that the leg holes on the side boards are on the same end and that the sides of the boards with the countersunk holes are facing out.

To put the frame together, you may need an extra hand or two. This person will line up the end pieces with the side pieces and make sure they are flush while the other person uses the drywall screws to fasten the sides to the ends.

Step 5: Attaching the Deck

Set the nesting frame into the standard board's frame. Make sure that the frame slides easily in. If it doesn't, re-check your measurements.

Use a 2x4 to draw lines around the outer edges of the plywood deck. These will serve as a guide for air-nailing the nesting board's deck so that you don't attach it to the standard board's frame

With the nesting frame in place, apply wood glue and smooth it out with a paintbrush. Lay the plywood deck onto the nested frames. Align the edges of the deck with the frame of the standard board. Use the brad nailer to fasten the deck to the nesting frame by nailing 3/4" to the interior of the pencil lines, leaving about 6 inches between each brad.

Be careful to hold the nailer straight up and down so that no brads stick out of the side of the frame. If any of the brads are sticking out of the wood, tap them in with a hammer.

Step 6: End Spacer Board

Because the nesting board's frame is made with a different size than the standard board, we must add a spacer board to the end of the nesting board that rests on the ground so that the in-play dimensions will be the same (especially if you're a stickler for the rules).

Lay a 2x4 on the non-leg end of the cornhole board and mark it so that its length will match that of the board's deck. Cut the board and find its center on the 4" side. Measure 5" to the left and right of center and make a mark. Measure 1 3/4" from the top of the board at the left and right marks. Make an indentation on both the left and right marks. Use a drill press to drill 5/16" holes on each of the marks.

Put a 5/16" drill bit into a hand drill. Set the spacer board on the bottom of the cornhole board. Clamp it to make certain it does not move and make sure it is centered. Use the holes made with the drill press as a guide to drill holes into the bottom of the nesting board's frame. Remove the spacer board and bore these holes out with a 3/8" drill bit.

Hammer two of your carriage bolts into the spacer board. This will be held onto the nesting board with two of the wingnuts when the boards are in play.

Step 7: Finishing the Nesting Boards

Next, you will return to https://www.instructables.com/id/How-to-make-Cornho... and perform steps 6-10. Some important things to note:

Bore out the leg holes on the standard board to 3/8" as these legs will have to be removable. Use wingnuts to attach the legs when in play

Hammer carriage bolts into the leg holes on the nesting board. Attach the legs using washers and nuts as these legs don't have to be removed.

Because the leg holes are in a different location on the nesting board in reference to the deck, you will have to perform step 7 on that Instructable for the nesting board as well to maintain proper dimensions.

After painting, on one side of the standard board, center and install a folding chest pull. Make sure that the pull folds toward the bottom of the frame so that it will be out of the way during play!

To hold the boards together during carry and transit, I make a strap out of webbing and sew-on velcro as shown above. You could do this with some sort of latch, but I used what I had on hand.

You can put the standard board's legs, the spacer board, and all eight beanbags between the boards before you nest them to keep the set together.

I hope you enjoyed this Instructable! Comment if you have any questions for me, or any suggestions! Remember, once again, the key is patience. Have fun!