Today I bought a baseplate, 10700. Sadly, the female connectors on the back are not "LEGO compatible"...you can't plug any LEGO bricks into them. I want to build a LEGO cart so dash can pull dot (a big mechanical moving robot can pull a small nonmoving robot). I need to plug the wheels on the bottom of the large brick and a fence to block the little robot in on top. I listed all items in category Bricks on Pick a Brick and found no match. Similarly for bricklink.
Where can I find a large flat brick (at a minimum 4 inches by 4 inches) so I can build a wagon?
If all else fails, I can superglue some thin bricks together.