Trot pokes before and after the jump. Focus on just trotting in for a while and get that perfect and relaxed. Then move to canter poles before and after the jump and repeat.
If you're not doing so already, I suggest sitting up very straight. Before the jump, you can circle your horse around the jump so they can get the feel of it. Maybe even dismount and walk them over the jump a few times if it's low enough.
ground poles, half halts, and stop and/or slow them to the trot or walk before the jump and make them think. don't always let them jump because they anticipate the jump so they rush ahead of you. make them listen to you so they know if they are going to jump or not
Depends on why your horse is bolting. If he is nervous/scared/unsure of the jump I usually ask them to circle, do some figure 8s, wall/trot transitions to get their mind back on relaxing and work. When I say I do those things I mean transitions while on the the circle or figure 8, usually you need only a couple of circles or figure 8s then proceed into the jump of the circle/figure. Repeat. Make sure the jumps are low or even just poles on the ground. If is excitability then canter poles/gymnastics:)
Try setting up gymnastic grids. This will teach him/her to slow down to be able to make it over the next jump. He/she might blow through the first combo, but will get the hang of it. This helped my gelding, who used to rush fences. I suggest starting with 4 trot poles, then 9ft to a cross rail. After you have worked through that until your horse is calm, add another jump 19 ft away. Repeat that process. Good luck!
Place poles on each side of jump for straightness, rhythm will come with seat and collection and then bolting, hold your reins and place stride poles
Place stride poles leading up to the jump