The hook is the second-to-last thing I do.
Put the strap under my instep, fold the gaiter around my leg, do the zip up (the zip is at the front of mine), press down the velcro along the zip overlap, there's also a press stud at the botton of that bit, then put the hook over the 2nd lace, then tighten the elastic at the top, above the calves.
It's a little bit of a faff, but most times that I need to put them on the conditions mean they stay on all day.