Tom,

If you already have an irregular cut you could look in Nick Schades book as was suggested (I've used it too) and cut out a cardboard shape. then lay it over your cut out and see if you have enough left to use it.

When I make a similar problem I start cutting battens or just use left over strips, bend them to fit in the hole you have cut and start removing where the batten touches. Of course to make the egg shape you need more of a flat across the back, you might clamp two battens together, overlapping in order to get an egg at the back.

This is a painful cut and try process at best but it will help you see where the irregular edges are.

There is no way to give simple direction here, it is just a way to start smoothing.
You might need several thicknesses of strips , especially to get the tight curves at the front and the back corner.

Be careful to not over cut one side. you probably need to get one side smooth, make a cardboard template and flip it over the centerline to cut the other side.

Can you post a picture?

Good luck.