Another idea is to use crayons, if the blocks are big enough. Then, put any kind of paper down on your ironing board (I used several layers of newspaper covered with brown wrapping paper so the ink won't rub off on the fabric), then your quilt squares or top, face up. Covered the portion you are pressing with several layers of paper towel, then press, not iron, the block with a medium hot iron. The heat fixes the pigment into the fabric and melts away the wax, which is absorbed by the paper towels and the brown wrapping paper. Keep changing the paper as needed until all the blocks are pressed.
If this is just the top, and not a quilt, you can cover the board it is mounted on with fine grit sandpaper. The sandpaper will grip the fabric and stop it from shifting and you won't have to stabilize the blocks with freezer paper.