Cook and shred chicken early. I generally boil mine since the sauce gives it plenty of moisture. Put the shredded chicken in a ziplock bag with lots of cilantro and lightly drizzle it with BBQ sauce. Shake the bag until the shredded chicken is coated. Just use a little to get on the chicken, but not so that it is sopping. Refrigerate until ready to cook pizza.
When you’re ready, either make the crust from scratch, buy a Boboli or those packet crusts. I’ve used all of these options, and they all turn out fine, so do whatever works best for you.
Once the crust is prepared, spread the BBQ sauce over it. This doesn’t have to be a heavy layer since BBQ sauce can be pretty strong and salty. Cover crust with cheese, then add the thin onion slices and chicken. Add more fresh cilantro over the top and lightly sprinkle with additional cheese if you wish.