This is a very simple but very effective coaster. I think it looks a bit beachy with the cord-like edging.

The pattern has both US and UK terms (UK terms are in brackets).

I used some old DK weight yarn I had in my stash. Use a yarn and a hook to suit each other (bearing in mind the finished size will change, of course).

I “tested” the gauge of mine by sitting a mug on it and seeing if it looked good.