First I train to hold still in hand. Then I lay the leadrope over their neck and pactise standing as I am beside them (maybe use this opportunity to check my emails☺)
When they have that down, I take few steps away.....or turn my back. Now my horses will stand still in their paddicks will I go into the barn to retrieve tack or grooming supplies. Its a handy thing to teach!
I'd work on ground work. Keep her moving, and when you ask her to stand, if she keeps moving around, get her going again. Standing and resting should be a reward! Also, spend time side passing/moving her hips/shoulders around on the ground over poles and around cones. This should transition over to standing quietly in the barn or wherever you two are. Also, correcting her as she moves is important, however I recommend not being too nitpicky. Spend time grooming/doing whatever your doing, and if she naturally shifts weight or moves a little that's okay. If she's swinging her hind around or moving when you're tacking up definitely correct it. Use the same cues you use in the arena when you're correcting her in the barn. Good luck!
You have your horse stand in a specific area and if he/she moves any direction, correct him. Do not let him get away with anything. Then, if you'd like, every few minutes that he stands, give him a small treat and praise him.