This is an adaptation of Catan-style hexagons, for an infinitely modular set of very simple roads! They are sized for the little Disney Cars cars, but work just great with Micro Machines as well.
There are two parts to these, the hexagon base and the plate where the road sits. To make contiguous roads, you'll need to match up the correct base with the correct plate, based on which type of road you're making.
The hexagon bases are setup to use 5mm magnetic spheres, which I find as a good balance of easy to install, no worrying about orientation, and a solid and secure snap. I know these are tough to find; sorry I don't have any advice there. I sacrificed an old set of Buckyballs (RIP) which were 5mm in size.
The plate and hexagon base need to be glued together; I recommend hot glue. Make sure you've got your magnets installed, the plate oriented correctly, and avoid gluing the magnet in place and you'll be good to go. With the plate securely glued in place, that will prevent the magnets from falling out. The glue doesn't need to be pretty, but you'll want to make sure to keep any glue off the very bottom of the hexagon, so they slide nicely onto your table.
The author remixed this model.
I used the hexagon base and plate core inspiration from these models, but they've been re-styled completely to support roads and not Catan.