Tools and supplies you need:
   Jointer / planer
   Compound sliding miter saw
   Table saw
   Drill
   Sandpaper (100, 150, 220)
   1x12 pine board, 4 feet long
   8 #8 wood screws, 2” long
   4 #7 wood screws, 1” long

I made it at TechShop.

To make the board square, I used a planer/joiner. I joined a face, then joined an edge, then planed the opposite face, and then joined the final edge.

Step 1: Cutting the Pieces

I then used to compound sliding miter saw to cross-cut the board into the following pieces (pictured above from left to right) and then trimmed them using the table saw:

A: Cross-cut to 12x16 (this piece will eventually be the top of the stool). I then used the table saw to rip it down to 10x16.

B: Cross-cut to 12x10; provided, however, that both end crosscuts were at a 15% bevel in the same direction (this piece will eventually be one of the two stool legs). I then mitered it into a trapezoid with the top 7.25” across at the short point of the bevel and the bottom 11” at the long point of the bevel.

C: same as B (the other stool leg).

D and E (pictured screwed together): 12x11.75 (first do a straight cross-cut to get rid of the bevel on parts D&E that remains from cutting out part C) (this piece will eventually become the stretcher and the subtop). I then ripped it using the table saw into 2 pieces, one that was 3.5” wide (part D, strecther) and one that was 7.25” wide (part E, subtop). I then went back to the compound sliding miter saw and mitered part D along both ends at a 15% angle (i.e. a trapezoid where the short edge is 10” and the long edge is ~11.75”). I then beveled the ends of part E at 15% in opposite directions so that it measured 10” along the long face (and ~9.75” along the shorter face)

I then sanded all the pieces, first using 60 grain, then 100, 150, and 220.

Step 2: Attaching the Stretcher and Subtop

I then placed the subtop horizontally (with long face facing down) centered on top of the stretcher (which was standing on its long edge) and used a 1/8" drill bit to drill 3 holes through the subtop and into the short edge of the stretcher.

I then used the drill to screw 3 #8 2" wood screws into the holes.

Step 3: Attaching the Legs

I then lined up one of the legs against the combined stretcher/subtop so that the short face of the leg was flush against the stretcher/subtop (and centered against the end of the stretcher) and the top (shorter) beveled end of the leg was level with the top of the subtop.

Next I drilled two horizontal holes (using a 1/8" drill bit) through the face of the leg into the end of the stretcher, one hole 1.75" from the top and the other hole 3.5" from the top. I then used the drill to screw 2 #8 2" wood screws into the holes.

Next I drilled two more horizontal holes (using a 1/8" drill bit) through the face of the leg into the end of the subtop, each hole 2" from the center. I then used the drill to screw 2 #8 2" wood screws into the holes.

I then flipped the combined piece around and did the same thing on the other side to attach the other leg.

Step 4: Attaching the Top

I then put the stool top piece flat on the table face down and centered the combined subtop/stretcher/legs piece upside down on top of it. I then drilled 4 holes (using the 1/8" drill bit) through the bottom of the subtop (near the corners) into the bottom of the top piece being very careful not to break through the top of the top piece. I then used the drill to screw 2 #7 1" wood screws into the holes (make sure to use the 1" screws, not the 2" screws).