Making simple wooden bar stools without a back is not a complicated task. First you will need your materials: wood, wood glue, clamps, screws, sliding bevel, protractor, pencil, saw, tape measure, plane, dowelling, sandpaper, small metal L-brackets for at least 2 legs per chair, stain and or clear finish and safety glasses.
When you have the materials that you will be working with you will measure the height of the bar, table or counter top these chairs will be at. It is recommended that a foot, 30cm, be left between the surface of the table and the seat of the chair. To accomplish this you will need to subtract 9 - 13in, 22 - 33cm, from the height of the surface of the table, take that total, subtract the height of the wood you are using for the seat, that total will be the length of your stool legs.
Then you will take the wood for the legs, measure and cut them to the correct length. Take a strip of wood the length of your seat and glue two legs to it this will give you a U-shape. You will need two of these leg assembles per chair.
The next step is to glue your leg assembles to the seat of your stool, once dry you will then put in the stretchers. Stretchers are the bars of wood between the legs towards the bottom of the stool and used as a foot rest and added stability. When you add the stretchers you want to do two opposite sides and when they are dry put the other two stretchers on. Doing it this way allows the wood to settle, giving the best support and stability.
If you think your stools may need to support a little more weight every now and then you can take the small L-brackets and attach them to your stool, one side on the bottom of the seat and the other on the leg. You can do two legs or all four this way, but is important to make sure your wood screws are not longer than the width of the wood. No one would want to sit on the tip of a screw or scrape their leg on a screw that hangs out of the leg. If you want to add some color to the wood you can add stain and a clear finish for protection.