Hi, this is my very first model. Pardon me when the dimensions are messed up.
I did export cautiously, and it is mesh fixed.

The most suitable dimension I have found to print this would be in X - 100 mm, Y - 100 mm and Z - 5 mm.

Do turn off the lock of aspect ratio when editing the Z axis alone, we don't want a thick coaster do we.

It fits small cups in the centre. Happy printing!