There are a couple of things that make this easier :

1. throw your trimmings from vegetables into freezer bags. Then freeze them until you have a day to make broth. Onion peels color broth, so don’t forget to save those.
2. concentrate the broth. Once you have the flavor you like, strain out the chunks and put it back on a simmer until there’s 1/4 to 1/2 the volume.
3. pour the concentrated broth into muffin tins and freeze. Pop them out and throw them in a freezer bag. You now have individually portioned condensed broth that you can throw in whatever you’re cooking.