I did it with the use of a rope, but without a saddle. My back started to hurt holding my horse's leg up, and I wanted a way to hold onto it without having to have him lay on my hand when he kneeled on the ground. So I had a rope around his pasture but I personally held the rope. I didn't tie it.
First I made sure my horse was fine with ropes on his pasture (thick rope lead rope, never tied it. If I had to let go I want it to fall off) So I ended up getting a lead rope wrapping it around his pastern twice and then walking around with it like that.
He was fine so I practiced holding it up for long periods of time with the rope to make sure he was okay with that.
Then I made sure his back up cue was effortless and he knew exactly what was offered and did it immediately upon offering.
Then I would hold up one hoof and ask for the back up. Soon as he shifted his weight backwards I would release and pat. Repeated that several times.
Then I would keep asking for the back up more. He got a release if he backed up a hind leg. (Wanted him to stretch out anyways). Repeat until he understood that he needed to move backwards even if his leg was up.
Then expect more and more. At certain points he would become confused and refused to move. I would just wait, continue to ask for the back up and hold the leg. Sometimes this would take up to 5 minutes, then he would move slight backwards and I would reward. I found it important that if he got frustrated or confused to reward any backwards movement to let him know that anything backwards was still good. Small tries get a reward.
Eventually you get to the point where they will go down one one knee. Don't keep them down. Let your horse get straight back up. Remember holding them down becomes more predatory behavior, and causes stress. In this process let them get up right away and praise.
Then ask them to stay down longer and longer, paying attention to their stress level. You stress them out by keeping them down too long they won't like it and it becomes harder to do.
The most important thing with stuff like this is to not do it for too long. I made that mistake when I was training and ran into more problems with Jake telling me "No more". Do small sessions, (max 10 minutes). Then go and do something else that is relaxing. Walk around, let your horse graze, lunge...something that does not require a lot of pressure. Then after 10 minutes go back to it. But only do a few short sessions then call it a day. All horses learn differently. Jake took 3 days to master it, my friend's mare took 3 weeks.
Some very important things. Do this only on soft ground (arena)
, REWARD REWARD REWARD. This doesn't have to mean treats (though I did use this half the time) it means you let the foot down, verbal praise and a pat, what ever it takes to let the horse know that they did what you wanted. Make sure you release the leg
. This is the biggest thing.