Wash the cabbage, carrot, beetroot, ginger, and garlic thoroughly.

Remove the outer cabbage leaves and set 2 large intact leaves aside for sealing the jar.

Thinly shred the remaining cabbage and transfer it to the large mixing bowl.

Grate the carrot and beetroot into the bowl with the shredded cabbage.

Finely chop the garlic and ginger, then add them to the vegetable mixture.

Weigh the prepared vegetables and calculate salt equal to 2% of their total weight; use about 32 g salt for 1,600 g vegetables.

Add the fine sea salt and spicy pepper flakes to the vegetables.

Massage the salted vegetables with clean hands for 5 to 10 minutes until they soften and release plenty of brine.

Pack the vegetable mixture tightly into the sterilized glass jar, pressing firmly to remove air pockets.

Press the vegetables below their released brine, leaving about 2 cm of headspace at the top of the jar.

Place the reserved cabbage leaves over the vegetables to keep all pieces submerged under the brine.

Close the jar loosely and ferment at room temperature for 7 to 14 days, releasing pressure daily if using a sealed lid.

Taste the ferment after 7 days and refrigerate it once it reaches your preferred tanginess.