You can influence a horse's development of good form, but IMO, you cannot create it where it does not exist. A good bascule is partly mechanical (ie, based on the way the horse is put together.) That said, you can set a horse up for success by teaching it to canter in balance, building jumps that encourage a good bascule, riding it accurately and so forth.
It's a bit like saying, "can you create a good mover?" Well... you aren't going to make a hack winner out of one that trots like a sewing machine, but you can generally improve one a bit with good training, teaching the horse to move correctly from behind, etc.
********** We move pretty fast for some rabid garden snails.
You can if it was naturally inclined to use itself well but was restricted by its ride. If it isn't naturally inclined you can improve it only slightly. It's a lot easier to destroy a good jumper than to create one.