The 10-1 shot faced a 20-minute wait before finding himself in the race after beating Reka Luna by a neck.
After a clumsy jump over the last River of the Moon Hurdles (11-4) and Tom Bellamy rolled across the track and the yellow car went with him to the far rail.
The trained yellow cars of Graeme McPherson and David Killahena always looked the advantage and kept their noses ahead on the straight to the line.
Slatter said: “He just kept sticking his neck out the whole way. He’s just really durable. Tom’s horse got away from mine and I just followed him. I don’t think anything will change.
“I didn’t hit him at all. I just followed him. Tom went after the last one and that horse loves a fight and I just switched. “
McPherson was always confident that the places would remain unchanged and he would retain the Grade Two event.
He said: “I know they were drifting down the track – it looked like Tom went over and ours followed.
“I don’t think Tom ever looked up from the front. Certainly from the last one it always seemed like we were head up, neck up. “
Killahena said, “I will be perfectly honest with you. He came here today off the back of the last run at Chelton and he had a fair chance and he went and got the job done.
“The thing about this guy is that he’s always saving, saving, saving. He never gets overwhelmed.
“Even from second to last there, you can still see there’s a lot left in the tank.”
Slatter was given a two-day suspension by the stewards for careless riding.
Co-trainer Matt Nichols called the error on Moon Rocket’s last, which he said was the difference between victory and defeat.
“He runs Blinder. If he jumped last, we wouldn’t have to go through 10 minutes of agony, would we!
“It was just a bit of green. He was off the reins going down to the last and had never raced before so he was looking around.
“It’s a shame, we were carried a long way across the track but there was no contact and I’m sure it’s a fair result.
“He traveled like a classy horse, but maybe he didn’t find as much as he looked likely, I thought he would go second last and win.
“He’s a nice horse to go forward with. To be fair, he’s not a Cheltenham horse, but Aintree and Cheltenham are pretty close this year, so we could probably look at Aintree. “