Ideally you move it to a "spot" on the ground.
Tapered insulation to build up the low spot, or, add a drain in the low spot, or, maybe cut out a channel to try to drain water away from the low spot.
I've done all of these things with varied results.
The biggest problem I have found is when you try to eliminate the low spot you just end up moving it to another spot.
We use these solar roof pumps. My son and I invented these, but sold the company last year. They work well.