I'm not the flood authority but it is my favorite quality in a flashlight, for my uses and I have been on a rampage trying to find them all for few months now.
I'd would say it's mostly about the reflector. Yes there are multi LED lights that make a nice flood too. And yes there may be optics that do it as well.
Maybe you could post some potential uses you may have in mind for this flood light.
I have a Moded 3w LED Minimag with McFlood reflector that does an excellent job. The L4 surefire is a nice wall of flood that is about 500 LUX and similar to an A19 reflector used with the Aleph system. The 5w LED makes a flood with a lot of output but when I use my 3w NG1000 in an A19 I get a pretty nice wall of light with extra throw, measured by about 800 LUX IIRC Now that's a wall of light. Others I can think of are the BlackBird but pretty much unobtanium.
Some would say the Jil is floody but its new reflector has a wider spot with lots of spill. Also the Q3 has a nice reflector that has a very gradual transition from the ceter spot to the outer corona. So it is smooth but not really a flood IMHO
Oh and try this if you want close or short distance flood and dont have a McFlood or McLux TK, Just remove the reflector in a minimag Mod or Jil. That makes a really nice flood. Smoothest flood you'll ever see.
If I think if any more I'll jump in later
Oh ya, forgot this other light I had. An Ombu 5w. It's a Nuwai clone that has a 5W LED and a Q3 reflector with two CR123A Batteries. That's more floody that the Q3
So in summary, reflector, 5w LED and ....
Forgot one other thing. I use an LDF lense on my Groovy! LED and one of my Magmod incan lights. You can get one at flashlightlens.com This can make any light diffused. Turns a thrower into a soft wide spot and sacrifices throw.
You can see some beamshot of the A19 in my sigline.