Rinse the cabbage, and remove a few of the outer leaves. Set aside the leaves. Quarter the cabbage, remove the stalk, and julienne. Peel and quarter the apples. Remove the core, and thinly slice.
Fill the cabbage 1 1/2-inches deep into a prepared fermentation crock, and mash until the juice is released. Add a few pieces of apple. Mix the salt, bay leaves, juniper, and caraway seed. Sprinkle a little of the spice mixture over the apple and cabbage. Continue layering and mashing the cabbage, apples, and spices until everything has been used. Enough juice should have escaped to cover everything. Rinse the reserved cabbage leaves, drain, and cover the mixture in the fermentation crock. Place a lid or plate on top to weigh everything down.
Cover with a cloth, and leave in a cool, dark place for 2-3 days until foam begins to rise to the top. Skim the foam, and store again for 4 weeks. After 1 week, skim the foam again. Repeat this every other day until foam no longer forms. When the foam no longer forms, it means the sauerkraut is ready.
The sauerkraut can be kept in the fermentation crock, or stored in screw-top jars.