Most of the free patterns I came across were quite large, so I just used the first few rows to make them coaster sized.
Rounds 1-6 of this pattern using specified materials
Rounds 1-7 of this pattern using No 10 crochet cotton and a size 7 hook
These first two are from patterns I found online, and the last is my own creation. Some lovely ladies from the 'Ville are testing the pattern for this, at which point I'll be posting it on here, C'Ville and Ravelry as a free pattern.