Scared ya??? Yes... I'm still here... (^_^;)
I made a lot of these coasters with worsted weight cotton yarn over months in the past, and I just wanted to share them with you all:
I just used Tunisian Simple Stitches(TSS) and edged them around with Single Crochet Stitches(SC). TSS and worsted weight yarn create the thickness just right for coasters. I also like how variegated yarn look in TSS. (^_^) Make sure to use a Tunisian crochet hook that is 1 or 2 size larger than suggested hook size for the yarn you are using to avoid excessive curling.