The first step is to cut the four sides of the drawer to length.
Drawers typically are built from one-by stock, but the widths can be dependent on the height of the drawer required. Rip the stock on a table saw to the desired width.
Then, cut the four sides to the finished lengths as required by the project's plans. Obviously, the two sides of the drawer should be the same length, and the front and back should be the same length.
For instance, for a drawer that will have a finished box size of 18" wide by 12" deep, you will need to cut two 18"-long pieces and two 12" pieces.