Once the tile is completely dry, cover with a layer of varnish. This will ensure the colours don't smudge when the coasters are being used.
Then, paint the edges of the tile white, or another colour that works with your colour scheme.
Finally cut a piece of felt just smaller than the size of the tile, and use the glue gun to attach it to the underneath. This will make sure no tables are scratched when they're being used!
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