Thank you everyone but I think I might try standing with the balls of my feet on a stair every for 2 mins
Stand with the balls of your feet on a stair every day for 2 min, and before you ride. It works, I promise
Also, you can just do some flat work and smal jumps with mainly focusing on your heels, but don't drop everything else. But has that as a focus if that's what you want, if that makes since?
I find that if my stirrups are always at the balls of my feet (that flat large part before your toes) then it is easier to press your heels down "to the dirt". You can also practice at home by standing at the edge of the stairs on your feet and pressing your heels down. A lot of it comes from practice and stretching your calves!