Sock pattern adjustment

I’d like to attempt the #100 white buffalo sock pattern for a man with size 14 shoe size. The pattern is a one size only and on the Internet it states must be adjusted for other sizes. How do I go about doing this and how would I turn the heel and knit the gusset if I add stitches I am using a 5 stranded wool very similar to the white buffalo I’ve adjusted needle size and still coming out too small. Any help would be greatly appreciated thanks

For the heel I do (French Heel):
50% of the stitches for the heel flap. That many rows slipping every first stitch.
K 50% of the heel flap +1 for the first row of the turn, ssk k1 turn.
Purl 5 p2tog p1 turn
K or P 6, 7, 8, 9 etc dec K or P 1 turn until all stitches are worked. Sl1 knit across.

If you do a different heel you can probably identify it here to get the percentages/numbers. http://www.socknitters.com/Tips/heels_by_the_number.htm

Pick up the slipped stitches (50% of the rows). M1 in corner. Knit around. M1, pick up other side.
Decrease every other round a stitch before and after the needles at the top of the foot.

Thanks for the info

Just in case you’re doing toe up I don’t know if the same flap, turn and gusset apply.