I've been asked to install some KIM Lighting well lights. The finished product will need to be flush with the finished concrete. I'm curious what methods people use to make sure the height of the well light is correct and how to make this well light's trim flush. It seems the trim sets on top of the concrete. I probably need someone who has installed these to answer. ?? KIM Lighting Well Light (http://www.kimlighting.com/kl-1900.pdf).
I've worked with these before, or something quite similar. We just packed dirt and/or sand under the light and ballast box until the top edge was even with the tops of the concrete forms. the light and ballast box had a white plastic temporary cover to hold back the concrete away from the top so the lid would fit down over the light and sit flush with the slab. It's also up the the concrete pourers to bring the concrete right up to the edges of the boxes evenly and not knock anything around. Hopefully you can supervise the pour. Hope it goes well.
As trublu stated, you should really wait until the forms are set before you place the wells. If the well is rated for use IN concrete at all, the manufacturer should provide some helpful tips for the particular model you are using.
As for securing the fixture for the pour, I've strapped them to the rebar as tight as possible, and, if the concrete guys don't mind, you can also pour a sonotube around the fixture and at least one of the nearby rebar rods for stability. Leave the top of your footer at least an inch or two below final concrete grade so as not to disturb final concrete finish. Most concrete guys I've worked with are pretty cool, and most will have no problem with this as long as you let them know ahead of time.