Oh, yummmy!!!
I have one alternative to cooking it all...but then there's the idea of melting cheese, but any ways....
I've used a tin can (taking the ends off of the green bean can) and set it on the plate you'll use.
Layer the ingredients (crab mixed with mayo or whatever, avacado, cheese, chopped veggies) until it's half way filled and packed down well---then remove the tin can and everything Should stay in one place. The opperative word here is "should". It's worked for me about 2 times that I've made it. It just looked like I actually did something fancy and pretty---and wowed my non-Atkins family