Yeah, normally your temp flange will be fitted/butted close to your body/pattern/plug and then any remaining gaps filled with wax or plasticine but clean and scrape it off square and sharp with a square corner tool. A light wax and clean then it's ready to mould. The mating flange will also finish sharp. This no help to you now though!

So your mould joins now appear as a "V" kind of hollow? this should be filled with wax or plasticine and cleaned off near flush with flat tool or blade. Then maybe a very light layer fglass across your mould joins just make the soft wax area firm and stable. Now follow though with your laminate set up for infusion.

The finished part will just have a fglass tape where your joins are. If you are intending a gel coat part then spray this down before the fglass but still fglass across the join areas on the gel coat so they are firm.

All this assumes you are not going for a clear cosmetic carbon part though?