just read through this thread. i find the best way of keeping the veg under the liquid is to fill the jar about 3/4 full, put a freezer bag in over the top, push it down to get the veg under the liquid then pour enough water in to weigh it down. it seems wasteful but you can reuse them.
my favourite recipe at the minute is this;
3 or 4 fennel bulbs, very finely sliced (i use a food processor with a slicing attachment); one onion either grated or very finely sliced; 2 cloves of garlic; a handful of good quality raisins.
massage the fennel and onion with a big heaped teaspoon of sea salt until it produces a decent amount of liquid (less than 5 mins, doesn’t take long). then add the garlic and raisins and give it a good mix. in the jar as described above, freezer bag in and leave it out for 7 days. then pack it in smaller jars and in the fridge.
you can also do red onions in a similar way, slice them up thin, add your salt, massage until you get liquid (takes a bit longer than the fennel, and you might need to add a tablespoon of sauerkraut liquid or water at a push), add some crushed coriander seeds then jar it with the bag on top for one or two weeks. this is more like a thick, sticky chutney once it’s done.