a little more intricate looking than the standard granny square.Looks like the wool eater blanket Bavarian Crochet.
Crochet Pot Holder Hotpad Free Patterns: A collection of crochet potholders and hotpads free patterns, square, circle, flower and animal.
Easy Crochet Project : Double Thick No-Burn Hot Pad – Live Well Utah
Adventures of a DIY Mom - How to Crochet a Hotpad - Super easy version!
Crochet - Ornamental Pot Holders (link to pattern)