The other day I came out of a good session to find that 3 of my futures box's have been damaged, while 2 of the are fairly simple repair one of them has collapsed about 20mm into the foam.
Ive been learning basic repairs on my boards for a little while now and I'm hoping that someone on here can give me some info on how I should go about it. The box itself is still intact and has had no crack to it at all. Last time this happened I took it to a shop (different fin box) and the bloke just built up a wall with resin.

That sux, and not easy to repair.

If the foam is EPS you can cut off the glass around the box and should be able to gently loosen the box from the foam to get it back in to position. You might need to cut some of the foam. Then you need to get some resin under the box to fill the void and hold the box in position. Use a syringe to inject resin under the box. You may have to drill a hole in the foam next to the box to do this. Sometimes it's just easier and neater to pull the box right out an then glue it back in position with Q-cell, chopped glass strands in the mix.
If the foam is PU (looks like it is), the box will have to be cut free from the foam as the foam usually won't let go. Then glue it back in as above.
Sand down the glass around the box (and the glass on top of the old box). Tape off the slot in the box and the screw hole. Laminate some cloth over the box, sand, and fill and sand.

Cheers Hunter, thanks for the advice.
It is a PU board, how do you suggest cutting the box out? Just with a razor?

A blade will do it, best with a utility knife like a stanley trimmer. If you are confident with a sander you can just sand around the edge of the box until you are almost down to the foam (be careful not to go too far), as you will need to sand down this glass on the board and remove the glass from the top of the old fin box before re-glassing the box anyway. This can make it easier and neater to cut the foam around the box as the glass layer is then mostly gone and not in the way when removing the box. Once the fin box is out of the board use the knife to cut the old glass free from the top of the fin box.

If you have a Dremel tool the little cutting wheels are also good for cutting the glass around fin boxes to remove them from the board.