I use those yellow plastic chocks, and they worked well on the legos. Since I have a twin axle, it is easier to do. I put the chocks between the tires, and depending on the slope, I place one chock on either side of ht trailer, then with the truck, put some weight on those chocks and have my wife slip the other chocks in place. When I put the truck in neutral and let the trailer settle, both chocks are now locked in. By the time we get the trailer leveled off, the tires are cool. I Utah where it was 100* by the time we reached our campsite after spending time in the office getting the paperwork done, they were cooled so I could chock them and put the X-chocks in.
The plastic chocks I have have ridges on the bottom for better grip and they seem to grip the lego blocks OK.
Camco Chocks