Fermenting
A lacto-fermentation covers a lot of ground: sauerkraut, kimchi, pickles, hot sauce, all use the same basic salt-and-time principle.
How it works
Vegetables are submerged in a salt brine (or salted directly, releasing their own liquid), which favours beneficial lactic acid bacteria over spoilage organisms. Keep everything fully submerged under the brine, exposure to air is what causes mould.
Safety
Use a scale to get the salt percentage right (roughly 2% of the vegetable weight is a common starting point), too little salt increases spoilage risk. A layer of white kahm yeast on the surface is generally harmless and can be skimmed, but any pink, black, or fuzzy mould means discard the batch.
Good crops for this method
CucumberCabbageCarrotBeetrootOnion & GarlicCapsicum & ChilliBroccoli & CauliflowerTomato