I found this very very handy little sock calculator designed especially for Opal yarns. Although I have not used it yet, it is a very very very useful wee tool. And now that I’ve linked it here I’ll never lose it. I imagine it will work for any 4ply yarn.

On that same site is a lovely rainbow ripple pattern, which I really must try.
And a great Simple Kid’s Sock.
Plus a cool hole pattern - as if you need to make holes in socks! It’s the “meg one” I particularly like.
All for Opal.
My Adult 4ply Top Down Sock Pattern
Cast on 60 stitches, dividing them evenly on three needles.
Join, being careful not to twist.
Work k1p1 or k2p2 ribbing for 15 rounds.
Continue in stocking stitch or pattern of your choice until piece measures desired length.
(Just working 8-12 rounds in k1p1 rib and then going straight to the heel makes a short ankle sock)
Begin Heel Flap
Work across 30 stitches (needle 1 plus ten stitches from needle 2 - keep them all on needle 1). Turn.
Now, working back and forth only on those stitches and turning the work each row:
*slip1 purlwise purl1* repeat to end of row (wrong side).
Slip1 purlwise knit across the row (right side).
Continue these two rows until you can count 14 slipped stitches.
End with a right side row.
Turn Heel
Purl 17 purl2together purl1
Slip1 k5 slip1 slip1, both knitwise, knit through front of slipped stitches.
Slip1 Purl until one stitch before gap, purl2together, purl1
Slip1 Knit until one stitch before gap, slip1 slip1, both knitwise, knit through front of slipped stitches, knit1
Repeat last two rows until all stitches have been worked.
Gussets
Pick up 15 stitches on right side of flap (needle 1)
Knit 30 stitches (from next two needles) onto instep needle (needle 2).
Pick up 15 stitches on left side of flap (needle 3).
Knit half the heel stitches onto this needle, put the other half onto the needle where you picked up the first group of stitches.
Knit one round even, knitting the picked up stitches through the backs of the loops.
Decrease Rounds
Needle 1: knit to within 3 stitches of end, k2tog, knit 1.
Work instep needle.
Needle 3: knit1, slip1 slip1, both knitwise, knit through front of slipped stitches, knit to end of row.
Knit one round even.
Repeat these two rounds until you are back to the number of stitches you cast on (60).
Foot
Knit around until 2 inches short of desired length of foot. You can use stocking stitch or continue in the same pattern established on the leg.
Toe
Decrease Rounds:
Needle 1: Knit until 3 stitches from end, knit2together, knit 1.
Needle 2 (instep needle): Knit 1, slip1 slip1, both knitwise, knit through front of slipped stitches, knit to 3 stitches from end, knit2together, knit 1.
Needle 3: Knit 1, slip1 slip1, both knitwise, knit through front of slipped stitches, knit to end.
Work one round even.
Repeat these two rounds until you have 20 stitches left altogether.
Knit across needle 1.
Graft toe together using magic kitchener stitch.
