For a vegetable based stock, I keep all my veggie scraps in a freezer bag (carrot tops, onion roots, potato peels, etc.) and when I get a full bag I make broth as follows:
I use an instant pot but a normal pot on the stovetop works. Add your veggies and 2-3 quarts of water. I also add 1 tbsp of each of these seasonings: salt, thyme, rosemary, and sage. Any herb works, just use what you like. (The important ingredient is the salt as unsalted broth is bland and tasteless.). Cook for one hour in instant pot on high or simmer 2 hours on stovetop. Keep a lid on the pot or your water will evaporate. Strain out the herbs and veggies and store in fridge in glass mason jars. Use or freeze within two weeks.