There's one crock pot trick that I've been keeping to myself for awhile now.
- Dump frozen vegetable scraps into crock pot.
- Fill crock pot with water.
- Cook on low for ~8 hours.
I let it cool then measure it into smaller sized Ziploc bags (usually 1 or 2 cups at a time) and then lay the bags down in my freezer, stacked on top of each other. Doesn't take up much room and they are ready to go when I need one.
Remember that the stock is unsalted- you can salt it before/ during crock-potting or you just wait and salt depending on the dish you create with it.