I've seen a number of bowyers who make longbows use the method 2Blade is probably describing, and I use it myself. An important distinction is that they are not "stepping on the tip of the limb," even though it looks that way. And the method they're using is not the step thru method, which could possibly damage the bow.
What they're doing is holding the bow by the handle with their right hand, pulling the bottom tip of the bow into the instep of their right shoe, while they push against the upper limb with their left hand and slide the string up the upper limb with the fingers of their left hand. The bottom tip either doesn't touch the ground or at least has no downward pressure against the ground.
For safety, keep your eyes lower than the upper bow tip when you're doing this in case something slips. I'm not sure how well this method would work on a longbow that is highly reflexed, but it works well on the straighter longbows I have.