I made these coasters in 2 parts that click together.
There is a groove in the bottom of the coasters so they stack neatly on top of each other.
The diameter of these coasters is 90mm.
The height of the coasters is 4mm (this is including the height of the black edge that is used to stack the coasters which is higher than the rest of the coaster)

The black part took 1hour to print and the yellow part took 15minutes to print.
I have also made the same kind of stackable coasters but with the biohazard sign.
Please check them out on my profile if you like these, they stack together with these ones.

No supports or brims necessary for printing.