I put together an enchilada casserole (which I will share sometime, because we made it up years ago and it's a staple) and a lasagna.
Easy-peasy frozen foodI would recommend eating frozen casseroles within a couple of weeks, or a month at the latest. You don't want to let them sit there for ages because they'll get freezer burn eventually.
** Before assembling, line a standard size freezer safe dish (like Pyrex) with some aluminum foil. I say standard size because this works best if the person you are giving it to has a dish in the right size. So 8x8" or 9x13" pans work well.
** Put it all together. Don't bake it! Pop it in the freezer uncovered until completely frozen (overnight is best).
** Take it out, spread some aluminum foil out on the counter and turn the baking dish upside down over it. The frozen casserole will pop right out. Wrap it up well with foil, tape it (I used blue painters tape, because it was sitting around) to make sure it's secure.
** Write clear instructions on a large piece of tape and place it on top. Basically, the lucky recipient just needs to take the casserole out of the freezer, remove the foil and place it in an oven safe dish. Allow it to defrost in the fridge overnight and then bake it as the original recipe recommends, but add 15 - 30 minutes extra because it will be cold. So the note on the lasagna reads "Vegetarian lasagna - Remove foil, place in a 9x13" dish. Defrost overnight in fridge. Bake at 375 degrees for 1.5 - 2 hours"