It depends what you are trying to achieve. A proper repair on that is going to be time consuming, quite skilled and probably expensive. Not meaning to be rude about the boat, but if you paid a professional it probably wouldn't be worth it.
Flocoat is like "gel coat" (which is not the same as paint - but is the outside, tough, water proof coloured layer on the GRP). Gel coat won't "set" if it is exposed to air (it is normally put in the mould first, then the grp laid up on top), so for use when you are adding it as the final layer people use flocoat - which is a mix of gel and wax - the wax separates to the surface and keeps the air out.
Mat is held in place with resin. Its not a trivial project for your first ever trip into the world of fibreglassing.
I've bodged similar repairs in the past using the "car body filler" approach. You've got a lot of cracking around that too though - which need exploring and probably grinding back and repairing too. The main problems with simply filling a patch that size and location is:
(i) you won't get a good colour match to the surrounding gel
(ii) you probably won't get a very good shape match to the surrounds.
(iii) supporting material whilst filling a big area is tricky (especially as you probably have no access to the underside).
(iv) getting good adhesion to the neighbouring material can be a challenge - in some places this doesn't matter too much - but somewhere than can be easily bumped is likely to just pop the big lump of filler out in one lump.