Using the techniques learned for staking a patio or walk, you can move on to forming and pouring a wall footing.
Strong, straight forms make the best slabs. Slabs that bulge, tilt, or otherwise display sloppy construction mar the beauty of your project. There's no easy, inexpensive way to correct faults in concrete once it sets.
Inspect each piece of form lumber before buying it. Look for knots, splits, and other defects that could affect its strength. Wet concrete will push the form with a tremendous amount of force, so the forms need to be structurally sound.
Make your 2x4 stakes long enough to put at least 8 inches into the ground when the stake is driven to 1 inch below the top of the forms (this keeps the stake out of the way when you screed the concrete). Slabs wider than 8 feet require control joints. These cuts in the surface of the slab keep cracks from spreading randomly across the surface. You'll cut them after the concrete is poured, but you'll mark their location on the forms before you make the pour.
After you build the forms, pour and tamp a gravel base to the depth required by code. Then lay reinforcing wire mesh on dobies or bolsters on the gravel.
About 4-6 hours to build forms for a 10x10-foot slab with curves
Sledgehammer, circular saw, hammer, carpenter's level, mason's line, cordless drill
Measuring, cutting, leveling, driving stakes, fastening
Lay out and excavate the site.
Deck screws or nails, bender board, expansion strip, construction adhesive, 2x4 and 2x6 lumber
Fasten level 2x8s to the stakes. (Use 2x8s even if the footing will be deeper than 8 inches because excess concrete that flows underneath the form only makes the footing stronger.) Clamp the forms to the stakes to make them easy to fasten. Reinforce joints with 1x scrap or 3/4-inch plywood.
Lay a level across the form to make sure both sides are at the same height. Adjust them by hammering the stakes (not the forms), if necessary. Fasten 2x8s to the ends to complete the form. Then add 4-6 inches of gravel, tamp it, and reinforce the footing as local codes require.
Reinforce the forms at 2- to 3-foot intervals with 1x2 spreaders tacked to the top edges. Then, starting at one end of the form, pour in the concrete, consolidating it by working a 2x4 up and down along the mix. To screed the concrete, lay a 2x4 (about 8 inches longer than the width of the form) across one end of the form and pull it along the length of the footing, using a seesaw motion as you go. Remove the spreaders and rescreed the concrete. Then let the concrete cure.