I scoured the internet for cool sandbox designs, but most of them seemed to require $200 worth of lumber, hinges, and unnecessarily complicated construction. I ended up designing my own, which is super simple, costs about $50, and only takes a few hours to build.

Final dimensions: 4'2" wide and 5'8" long with 12" sides.

Materials You'll Need:

Three 8-ft 2x12s ($12 each at Home Depot)
One 8-ft tree stake ($5 at Home Depot)
One 6-ft square of landscape fabric ($8 at Home Depot)
1/4 yard of play sand (~$8 at your local landscaping supply)
Staples, nails, optional paint and decorations

Tools You'll Need:

Saw (a circular saw would be adequate, a table saw and chop saw will make things slightly easier)
Hammer
Drill
2-inch hole saw ($14 at Home Depot)
Paint brush

Step 1: Cut the Boards

Cut the 2x12s at the angles and lengths shown in the diagram and make sure everything lines up.

Leave the brown piece for last. Rip it (cut it in half lengthwise) so you have two 2x6s instead of one 2x12, then cut the correct angles.

Use the hole saw to drill a 2" hole in the center of each brown board (for the mast).

Step 2: Sand and Paint the Boards

Do a quick sand with 60 or 80 grit sandpaper followed by two coats of outdoor paint or stain.

Step 3: Nail It Together

I used galvanized 8d 2-1/2" nails, but anything long enough to reach through the boards will probably do the trick. Drilling pilot holes before nailing will minimize your chances of splitting the wood.

Step 4: Optional: Add a Seat

Theoretically you could have measured and cut this piece beforehand, but it's easier (and probably more accurate) to trace the angle after the ship's put together. Just lay a scrap from your 2x12s across the ship's front, trace the outline, cut it out, sand, paint, and nail it on.

Step 5: Staple in the Landscaping Fabric

Lay the landscaping fabric in the bottom of the box, staple it to the sides, and trim the excess. This step isn't strictly necessary, but it will keep your sand from leaking or getting dirty.

Step 6: Add the Mast

Cut off the pointy end of the tree stake and sand the whole thing down.

Slide it into the holes you drilled in the cross-pieces. Use a few screws or nails to keep it from sliding out if you like.

Step 7: Fill It With Sand, Decorate It, and Enjoy

Decoration ideas:

Vinyl-cut portholes
Laser-cut and paint letters for a name
Sew a pirate flag and put it on the mast

My five-year old and one-year old, along with their cousins and friends, have spent countless hours using and abusing this sandbox for the past several months, and other than some scuffs on the paint, it's still in great shape and still gets played with quite a bit.

Thanks for reading!