Sock Expansion Question

Hi, I’m a fairly new knitter and I have a qestion about socks. I have a pattern for a pair of felt slipper soskc, but it’s for medium sized feet. I would like to make them for my mom, but her feet are large [size 12] and I’m not quite sure how to alter the pattern to make the socks the right size. Could anyone offer any advice? Here’s the pattern:

CO 44sts [Cast on loosely! I cast on over two needles held together].
Join, being careful not to twist the work and place a marker at join for beginning of round.
Knit every round in st st for 3 inches [or longer if desired].
[on 22 stitches]

Knit 11 sts past the marker, then turn and work back over the stitches you’ve just worked [ignoring the other 22 stitches on your needle, which will be held to become the instep] and
Heel Row 1: sl 1, p 21, turn
Heel Row 2: s1 1, k 21, turn
Repeat these 2 rows 11 more times or until the heel flap is about as long as it is wide.
Continuing on heel stitches only:
Row 1: p 13, p2tog, p1, turn
Row 2: k 6, k2tog, k1, turn
Row 3: p7, p2tog [1 st from each side created during the last turn], turn
Row 4: k7, k2tog, turn.
Repeat rows 3 & 4 until there are only 8 sts remaining of the original 22 heel stitches, with no stitches on either side of the decreases.
The last row should be right side row.
Now, you’re going to connect this lovely heel you’ve just knit to the rest of the stitches in order to knit the rest of the foot in the round.
Pick up and knit 12 stitches from the right edge of the heel flap, place marker [Marker 1], k22 sts that were being held for the instep, place a marker [Marker 2], pick up and knit 12 stitches from the left edge of the heel flap, then knit 4 sts from the heel, place yet another marker [Marker 3] or a safety pin to mark the new beginning of the round. The remaining 4 heel stitches will be the first 4 of the next round [ 54 sts].
[to decrease those 54 sts down to the original 44 sts]
K 1 round plain over all stitches, slipping the markers when you come to them.
K to 2 st before Marker 1, k2tog, slip marker, k to Marker 2, slip it, ssk, complete round.
Repeat the last two rounds 4 more times [44 sts].
Knit around in St st until work measures 9 inches* in length from back of heel, then begin toe decreases:
*For different sizes: Take the total length of recipient’s foot and multiply by 1.3 to determine the required total length of sock before felting. Then determine length of sock to knit before beginning toe decreases by subtracting 3.5 inches from total required length.
Round 1: K to 3 sts before Marker 1, ssk, k1, slip marker, k1, k2tog Repeat from * to * with second marker.
Round 2: K around without decreasing.
Repeat these last two rounds until there are 12 sts remaining.
Divide sts at the markers onto two needles [6 stitches from top half of sock on one needle and 6 stitches from bottom half on the other], break yarn leaving 12 in tail and graft the toe closed.
Weave in any ends using tapestry needle.
Felting slippers to size
I felted the slippers shown here by running them through the wash cycle of my washing machine set on 40 C [105 F] with a tablespoon of a mild liquid soap and a towel for added agitation. It is essential to check the status of the slipper every few minutes and stop the agitation process when it reaches the desired size.
Rinse to remove the soap residue and spin to remove as much water as possible, then either form to shape and leave to air dry or put them on over another pair of socks and walk around for a while to let them form to your feet perfectly.

I think a lot of the felted slippers are a sort of felt-to-fit type deal, so I’d just felt them a little bit less so they stay a little bit larger - if you’re making them to felt, they should knit up to be larger than a large anyhow. Just keep checking on them every couple of minutes until they’re the size you want! :smiley: That’s just what I’m thinking, but maybe someone else could give you more precise instructions.