I am calling these toasty extra large socks / slippers “Study Buddies” They are made from 100% Canadian wool from New Brunswick.
You will need about 300 grams of 5 strands pure wool Country Roving from Briggs Little (my personal choice).

I used 10mm circular needles:

cast on 28 stitches (the blue in the above picture) knit in garter stitch for 40 rows
loosely cast off

the piece measures about 14 inches (35.6 cm) long by 10 1/2 or 11 inches (27 0r 28 cm) wide.
If you like you could change colours (in above picture -the grey)

pick up 8 stitches at the end of the 14 inch length
you want the 8 stitches to be in the middle, so you should have 7 stitches on each side of the 8 stitches.

inside view of the Study Buddy!

with the right side facing you knit 21 rows (of the 8 middle stitches just picked up) ending on the inside (leave on needle).

with the inside facing you pick up the 7 stitches on the right (from the blue end) and 10 stitches along the right of the 21 rows of 8 stitches you just knit (the grey).

knit across the 17 stitches (just picked up) plus knit across the 8 stitches remaining on the needle.

pick up 10 stitches along the left side of the 21 rows of the centre piece (grey) and pick up the remaining 7 stitches on the left (blue). knit across these 17 stitches

you should now have 42 stitches in all.

continue in garter stitch until the sides measures 1.6 inches (4 cm).

next rows:

knit 2, knit 2 together, *knit 4, knit 2 together* -** 6 times
knit two – you now have 35 stitches.

knit 2, knit 2 together, *knit 3, knit 2 together* -** 6 times
knit 1 – you now have 28 stitches.

knit 1, knit 2 together, *knit 2, knit 2 together* – 6 times
knit 1 – you now have 21 stitches.

loosely cast off.

using the corresponding colour of wool, sew up the bottom of the foot and the back of the leg (within 2 inches of top).
fold down the two inches at the top of each sock and tack in place.

These Study Buddies could be used in your boots, or inside when lounging around.

If you prefer a less bulky Study Buddy use – Patons Classic Wool bulky 100% wool. Not as warm or heavy, but still a nice toasty sock.