There are three sizes here.
The directions call for you to start fashioning the slippers at the heel, making a small triangle and then casting on stitches to make the sides.
So it will look like a rectangle with a triangle on one end and decreases for the toes on the other end.
But I was just talking with Grandma's sis-in-law this weekend and she said Grandma didn't 'do' the triangle bit. Yet I love it because of how the slipper feels and because... Grandma wrote the pattern that way.
It takes me about 1 night to knit a man's slipper.
Work initial section in garter st. (knit each row) I use a Phentex yarn for my first wool selection and usually a variegated acrylic for the second yarn. This means I have to grit my teeth and shudder the whole time I am knitting. But if I don't I have to knit us new slippers each month and I like knitting other things!
For a man's set of slippers I need 2 balls of Phentex (I don't know the yardage or weight) and 1 super saver size acrylic. But often I get two just in case and return the second.
I can easy get an average pair of child's slippers out of 1 phentex, 1 acrylic.
Sizes: Child, Woman, Man
With Double Wool and size 5.5 mm needle cast on 4 sts. (note I use long tail method and leave a really long tail so that I can use that tail to stitch up the heel when finishing off the slipper)
row 1: knit
row 2: increase each end knit (increase front and back of sts)
row 3 & 4: knit
row 5: increase each end as before and knit rest of sts
keep knitting 2 rows and increasing on the third... but if they have a smallish foot, you can monkey around with this. Sometimes, if they have a narrow foot I will increase every other row or increase for rows 2 & 3 and knit 4, etc. And sometimes I cast on 6 sts.
Repeat increasing until 10 sts on needle for child, 12 sts on needle for woman and 14 sts for man.
It is okay to end on an increase row. Cast on 9 sts on edge for child, 11 for woman, and 13 sts for man.
K cast on sts, P 1, K to last sts, P1 and cast on same number of sts for other side of slipper.
For total of 28 sts for child, 34 sts for woman, 40 sts for man.
Next 2 rows:
Row 1: K all sts
Row 2: K (9 for child, 11 for woman, 13 for man), P1, K (8, 10, 12), P1, K (9, 11, 13)
Repeat these rows for about 2/3rds of the desired slipper length. Grandma would hold up the knitting to the bottom of our feet and stop this repeat once the slipper hit the ball of the big toe.
End this section after a row 2.
Row 1: K 2, (P1, K1) 4 (child), 5 (woman), or 6 (man) times, K (9, 11, 13), (P1, K1) (4, 5, or 6 times)
Row 2: (K1, P1) (5, 6, or 7 times), K (8, 10, or 12 times), (K1, P1) (5, 6, or 7 times)
Repeat until nicely even with the big toe. I do this until the 'fat' part of the big toe, basically you've got 3 rows left so till you've got the length you want. The three rows tend to give the slipper dimension since your feet aren't flat.
If you want a tighter slipper stretch out your knitting to see how it fits. If you are like some members of my family and don't want tight slippers, knit till the tip of the toe then do the decrease rows.
Row 1: K2 tog across row.
Row 2: Purl
Row 3: K2 tog across row.
Break yarn with nice long tail. Thread through remaining sts. and use tail to sew up the centre seam right to where you started the ribbing pattern.
Note: I transfer the sts to the other needle and then pass the yarn through all the sts loosely, then do it once more and pull tight. That way I have a nice strong close at the toe. It looks like a star. Then I flip the slipper inside out and mattress stitch or even just zig zag up the very edge of the knitting. It looks decent enough and is flat enough not to bother the wearer.
Once you've finished the toe end, you have to sew the cast on edges to the triangle part to make your heel.
I usually go in a row because the cast on sts are wonky and tend to stretch too much with wear. Or if I've left a long enough tail I double stitch back over the first seam to enforce the first seam.
Typically, because I've used 2 strands I use 1 strand to stitch up one side and the other to stitch up the second side.
One last tip... write down how many rows of each section you are doing. I write them down as garter rows, since you will keep the centre part of your rectangle in the garter stitch and it is easiest to count.
When it comes to repeating to make a matching slipper you can then easily make a second slipper.
A slipper for my husband or brothers tends to have 45 garter stitch rows plus the 3 decrease rows at the end.
My slippers (size 11 1/2 ladies) has 30 rows. and my children, who are incidentally very tall for their age, have about 20 rows.
My mother had about 20 rows, but with the woman's width.
I apologize for any errors and will gladly take correction. Part of my understanding of this pattern is from having watched Grandma knit.
Oh and my Great Aunt said to just cast on all the sts at once instead of the triangle. I won't, but... you could!