Costco (in Canada at least) has these sweet rubber mats that remind me of the gym. Way cheaper than Amazon since they are heavy as heck! It's flat on the other side :
Supreme Garage Floor Tiles, 8-pack | Costco
Ultralock Black Solid Garage Tiles | Costco
AutoFloorGuard 8.5'x20' SUV/Truck Vehicle Containment Mat | Costco