Is any prep required to lay these mats down on my garage floor? I wanted to create a 12' square.

The only prep you will need to do before installing our Extreme Mats is to make sure the subfloor is clean and free of any large dirt or debris. You will also want to make sure your subfloor is flat as well, so if you do have any major divots or pits, you may want to fill them before installing the mats.