At our size and reynolds numbers I'd suspect not a lot. The function of the slot is to direct high speed air over the leading edge of the flap surface and in effect produce a "blown" surface that is resistant to stall so it can more ably direct the upper surface air downwards. But at our sizes the air does not flow the same way through a scale gap as it does through the full sized versions. And most of us lack the wind tunnel needed to develop a working slotted flap that will be effective in our sizes.

But all is not lost. If you just copy to scale the original system the gap may or may not help but it most likely won't hurt. If it doesn't work as intended then your flap will act like a plain flap and that's not so bad either.

As for hinge design and any associated tracks or other hardware you'll need to ask about options in another forum that's related to such things.