Hot spots on your feet tend to come from two basic sources: friction heat from the rubbing of your foot against the shoe/boot, or retained heat.

Friction can be caused by a) heel-lift from a too stiff shoe/boot, or b) the shoe/boot is too loose, allowing your foot to "slosh" forward and back or side to side, or c) a too tight shoe/boot that presses too much against your foot at some points.

Retained heat comes from the calories you burned from exertion which cannot escape the shoe/boot. Hands and feet tend to be the places where the body wants to rid itself of excess heat. We evolved that way. But that strategy doesn't work when your footwear traps the heat your body is trying to throw away.

Leather boots are unfortunately much more prone to all these causes of hot spots and blisters than fabric-upper trail shoes are. If you must wear a leather boot, the only remedy is a near perfect fit and the correct socks that help to minimize heat and friction. Plus, it helps a lot if the weather isn't too hot.

The selection of leather hiking boots is getting smaller all the time, and the knowledge of what designs work best is being lost, in favor of cost-cutting and marketing gimmicks. I wish I could tell you what to do, but your best option is to keep looking and looking until you find a boot that feels like a glove on your foot, then use a slick, thin nylon liner sock and a lightweight wool sock over it.

Good luck.