Bulk food preparation for the freezer - ideas?

I have a slow cooker and am good at making soups and stews for the freezer, and sometimes I freeze lasagne or macaroni cheese (not that the last two usually get left long enough to be frozen!), but I'd like some ideas for meals that can be partially prepared and then frozen, or ingredients for savoury dishes that can be prepped and frozen to be used later.

I've frozen strips of capsicum when they are at their cheapest so we can have them in winter, but not really tried anything else. Would something like chopped onion freeze well or would it turn into mush when thawed! What other vegetables freeze well! What needs to be avoided at all costs!

Any other ideas!

We have a small chest freezer that mostly contains loaves of bread and bags of ice cubes - I'd like to put it to slightly better use now that I'm learning how to cook properly :-)

we've just made 5 pizza bases, and we also made the tomato base in the crockpot, and put into freezer bags

I used to batch cook meatballs in the microwave (in a circle on large plate) and then free-flow freeze. They can be taken out & browned up or thrown into a sauce etc.