I cant remember whether or not you have a school, or some poles?
I have taken Ella in the school for a leading lesson. I mean, me teaching her to be led nicely.
If you have some poles, walking up and down through poles laid parallel on the ground. Or poles can be laid out to create an S shaped maze and one leads the horse through this in walk, poisitioning the feet so they remain witin the poles. This comes from Intelligent Horsemanship. Kelly Marks may have something on line.
Michale Peace would start every demo by leading the horse in walk, Halt walk transitions, expecting the horse to stop when he did. If the horse came too far forward he would come in front of it and back it up and then walk again till the horse stopped excatly whenb he did. The he began to lead round obstacles and over a tarpaulin. I dot feel able to do more with Ella but Peace used umbrellas and goung through narrow spaces.
I have a book which is a sort of anthology of ground work.
It gives ideas fron a selection of trainers and I preferred to use the trainer's own books - however it is a good taster and if you like a particular trainer, there is Youtube - so much is now on line.