The last set of coasters I designed - Citrus Fruit Slice Coaster I gave to my mom and sister and wanted a set for myself. Since I live in New York and it's springtime I opted for a flower design. These are printed in flexible filament (TPU). It won't scratch your furniture and it is super sturdy and durable. They are even dishwasher safe.
To insure a nice looking top surface use 50% infill and extra top and bottom layers.
Some slicers will allow you you pause your print and switch filaments. That's how you get the two color effect. The slicer I use is Cura. Wait until you can make out the petals and a layer of fill - I use a spatula (print removal tool) to catch any oozing.
3d printing enthusiast specializing in flexible prints. Check out my flexible designs here on this site and my posts on Instagram and Twitter.