Sweep out the bottom of the closet. You will need a completely clean surface to add flooring. If necessary, use a shop vac to clear out any debris.
Apply vinyl peel-and-stick tiles. Start in the center of the closet and lay the first tile. Peel off the adhesive backing and press the tile firmly into place. Finish this row and then start the next row. Use a utility knife to trim the edge tiles as necessary.
Apply carpet tiles. Instead of using regular carpet, you can use peel-and-stick carpet tiles. The installation process is much the same as for vinyl tile. Start with your center tile and lay out the remainder of the row. This tile can also be trimmed with a utility knife to fit.
Install cedar wood flooring. You can make your own cedar closet by laying down cedar wood flooring. You'll need a nail gun to make this process simple. Use a stud finder to locate the floor joists. Lay down a board and nail it into place over the joists. Repeat until the entire floor is covered.