There's a trick to this. Put one hand under the mat and lift it to the contour of the hook, one hook at a time, while pushing the hook in using the other hand. Comes right off easily.
Yes,, unfortunately we are all suffering because someone let their mats get all bunched up and interfere with their accelerator or brake. If you have some dirt or grass or pebbles on the mat and you want to get the mats out to get rid of it without bringing out the wet-vac, good luck! By the time you have negotiated the plastic hooks all that dirt is under the seats, on the carpet and even on the seat itself. It took me five frustrating minutes to release the mat a couple of days ago. I tried one hand under, both on top and every possible combination. My hook must be bigger and/or my grommet smaller.
I checked out Biglots, and found a multipurpose utility/automotive 3x5 carpet fabric as well. My car has the dark gray cloth interior, and the dark gray color I found there matched it pretty well, as long as you didn't put it side-by-side with the interior cloth. If I were to do it again, I'd cut the matt/carpet wider by half a centimeter on each side, since there is actually extra space width-wise when you place the cutout into the car. Otherwise it worked out great!