How to make a concrete bench
Part 1. Making the form
Step 1.1 Cut and assemble the edge frame of the form
The form is the mold or the boxing that holds the wet concrete in place until it sets.
The two (c) pieces and the two (d) pieces are of 2" x 4" (100mm x 50mm) stock. They can all be cut from one 11ft (3.3m) length.
Before you cut the individual pieces to length, make a 10° angle cut (chamfer, bevel) along one edge of the wood, as shown in the drawing.
This is best done on a bench saw with the blade tilted 10°.
With a certain amount of skill, it can also be done with a circular power saw with its blade tilted 10 degrees.
Then cut the two (c) pieces and the two (d) pieces to the dimensions given in the drawing below.
Note: The drawings below show the wider face of the wood. The beveled edge is the bottom (lower) edge of the pieces in the drawing.
Then, glue and nail or screw the (c) pieces and the (d) pieces together in picture-frame fashion.