If you sew the 3" X 3" piece to the 3" X 2 1/2" piece, they would make a 3" X 5" piece.
If you had three 2" X 4" pieces sewn together, they would make a 4" X 5" piece.
Then you could sew the two units together to get a 5" X 6 1/2" rectangle (4 1/2" X 6" finished).
Turn the blocks different directions to make a design.