This is a variation on the traditional Grandma’s Slippers, starting at the back of the heel with . You join one side of the cast-on and knit it as if you were knitting a flat project. Once you have knit a few rows, you will see the back and the foot of the slipper start to form.  Here's a on this variation to Judy's Magic Cast-On. 

• Yarn:​ (50% alpaca, 50% wool; [131 yards 120 meters]) 1 to 2 skeins.  An easy care option is
• Size:  S/M takes 1 skein and size L takes 2 skeins.
• Gauge:​ 18 (16) stitches and 38 (32) rows = 4 inches in garter stitch blocked.
• Circular Needles:​ Size S-M, US 6 (3.75 mm); Size M-L, US 8 (4.5 mm)
• Notions:​ Markers, tapestry needle
• Finished size:​ S/M = 3.5” wide X 7.5” long, L = 4.5” wide X 9.5” long
• Pattern only!