Felting questions

I have some Lion Wool that I want to use for my first felting project. I decided to keep it simple and make a pot holder.

Does garter stitch felt well and if so is it thicker than stockinette after felting?

I know it’s not something that can be answered precisely, but should I make it twice as big as I want the finished piece? Or would one and half times bigger be a better idea?

ETA Does stockinette still curl after felting or if laid out flat to dry will it stay flat?

When knitting a purse that was felted afterwards I remember that we used big needles and it turned out big enough to hold a toddler before felting.

I found this http://www.purlbee.com/2011/01/23/whits-knits-four-felted-hot-pads/ and decided to go with garter stitch. Based on their gauge and cast on number and after felting measurement I cast on 50 sts with my worsted weight yarn and started knitting. I’ll find out how it works eventually. I’ll be hand felting it.

Big enough to hold a toddler. I think I’ll need lots of yarn when I make a bag.