From the website:

I have been looking all over for a pattern like the slippers Aunt Maggie and my mom used to make and I finally found one in an old pattern book from the 40’s, and I have posted my adaptations to make it easier!

There is no specific yarn called out for in the pattern, any worsted weight will do. It can be used single or doubled. Using a double strand of worsted weight is recommended by the author.

Gauge:

1 strand: 4 sts and 8 rows = 1 inch on US9 needles

2 strands: 3.5 sts and 7 rows = 1 inch on US9 needles

These slippers are knit flat and seamed at the instep and heel.