This 12" high child's wood stool is easily made using stock dimensional lumber (standard or closest metric size) all cut at 90 degrees and assembled with glue and nails/screws. The overlapping joint technique is simple, direct, and strong. It's versatile and adaptable to many designs -- see my blog for lots of other stuff. http://furnituredesignbank.com
Step 1: Exploded View
Use this exploded view to create your cutting list. You can make this stool longer, more bench like, or even deeper by using different stock lumber seat planks -- like1x3's for example, and then there's plywood or anything handy and recyclable -- it's the overlapping joint that counts.
Step 2: Tools
I used a chop saw, but a hand miter saw and a little elbow grease will also do the job. A saber saw can work if you can make a straight cut; I never can seem to do a great job with mine. The more clamps the better. I used 1 1/2” wire brads, but 3d or 4d finish nails are good. I
also used #6 square drive wood trim screws to attach the side skirts, but nails work there, too.
Step 3: Cut, Sand & Mark
Sand/ease all exposed edges now. Mark the ends and best faces. Drill any pilot or clearance holes to prevent splitting near the ends.
Step 4: Make Two Leg Assemblies
Clamp a long stop block to a bench and use a smaller free block on the sides to locate the legs and skirt flush.
Step 5: Check the Square
This is an important step which will save you grief later. Do it immediately while the glue is still wet. You can usually budge the legs a little. And wipe off any excess glue while you're at it.