Start out by measuring and cutting all your stock according to the cutting list and set it aside. Take the legs and mark out the tapers. The taper starts 20 "up from the bottom. The leg tapers to 3-1 / 2" at the bottom. Repeat for all the legs and cut out.
The legs join the main stretchers at 75 °. This cut is best made with a circular saw. Mark your lines, clamp the stock on edge and cut. Flip the stock over to the other edge and make the through cut.
Time for some assembly. On the main stretcher mark a line 1-1 / 2 "from each end. This is the outer face of the leg. Now make a second mark in from one edge 1". This is the top of the leg. Do this for each leg on both stretchers.
Apply some glue to the angled side of the leg and position on the marks you just made on the stretcher. Secure with 4 – 2 "screws. Repeat for all the legs.
Position the 3/8 "plywood braces on the outside face of the legs butting into the bottom face of the main stretcher. Scribe the angle onto the braces with your pencil and cut. Braces with 6 screws, three into each leg.
Now draw 2 lines down the length of each top step, offset 3/4 "from center. Countersink 5 holes, 3/4" deep in each step. Alternate the holes on each side of center. Position the top onto the stretcher flush with the ends. Secure with screws only.
Finally secure the lower step midway up the leg using screws & adhesive.
That's all there is to it. These saw horses will easily take the load of a lift of plywood or studs. Plus the make a great scaffold. Space about 8 'apart and secure a 2 x 10 between them.