I finally remembered to take some pictures while making a stool to share a tutorial with you.
First decide what you are using for your top. I have been using two 2x6's, which make mine about 18x11 (these shown area little smaller--they were a special order to fit under one of the tables I had made).
Then cut 2 pieces of trim board or 2x4s 2 inched shorter than the length of your top.
I set these on the top and then measure what I need for the shorter side pieces. I have not been doing mitered corners because I use trim boards and it is too thin. I assemble the apron or frame with the nail gun. Since I screw the legs in from both sides, this doesn't need to be solid.
Then cut 4 2x4s for legs, mine have varied in height, but usually 12 inches.
Lay frame upside down on a flat and level surface. I screw legs in with 2 screws in the front and one 3 inch long screw from the side.
I paint and sand all pieces separately. Because I use trim boards I have a very narrow space to drill through to attach the top. I set the top pieces on there to get them in the right place and then take 1 piece off so I can see exactly where to drill.
And there you have it, a simple, sturdy stool, and for me, all made from reclaimed wood!