A quick Google image search for "tetris solved" returns the block layout shown below. This design (or any other design where the tetris pieces fit perfectly together) will return the maximum amount of tetris pieces with minimum space wasted. As you can see from this design (5 blocks x 8 blocks) 40 wooden cubes will be needed.
Making the cubes:
1. Cut the 1" thick board into 1" wide strips. Further cut these strips into the 1" cubes necessary. A table saw and chop saw make creating the cubes much easier. I recommend making a few more cubes than necessary to have extra (just in case).
2. To form the "classic" tetris block shape we will sand off the corners of each of the cubes 1/8".