EZ Seiza Bench
I've been using one of these for years. It's the best.
Make the top out of something stiff like 3/4" plywood or oak.
Make the legs out of 2X6 framing lumber.(1)
Attach each leg at the sloped end.
Centered at 1 1/2" from the ends of the top.
Use nails or screws or whatever you have.
I like to use construction adhesive (Loctite PL Premium is nice).
Smooth the edges and sand it.
Leave it unfinished or paint it or something. I like to use a light coat of boiled linseed oil.
Maybe stick a little pillow on it.
1) After using the same bench (the "tall" version) for about 8 years I decided that it was too low. Raised it an inch (Screwed some wood onto the bottoms of the legs).
2) Well that didn't work too well. The edge of the top bites into my leg a bit and it's just a little awkward. So I removed the risers. Put a pillow on top.
3) Ok that isn't quite working. I'm going to make a new bench. I think that a process for fitting custom benches is called for. I've tried a stack of books with a board on top and that kinda works but what we really need is a doodad with adjustable tilt and height. Or maybe I'm just getting fat.
4) Homestyle bench fitting jig.
5) My new bench. Slightly different tilt. Legs are 5 5/8, 7 3/4. All coarse red oak. 6 3" construction screws. Barely sanded. No finish. No pillow. Splintery. Fits very well. It's the tilt. The tilt is important.