Gather all the supplies and ingredients. Clean the equipment and let them air dry, keeping the surfaces free of bacteria. You can sanitize your jars and lids in boiling water.
Wash the vegetables.
Using your sharp knife, shred the cabbage into thin, small slices.
Shred the onions with your knife by slicing small, thin slices as uniformly as possible.
Shred the carrots. A cheese grater works well.
Add all the vegetables, oregano, crushed red pepper, and sea salt to a large bowl.
Mix the ingredients. Make sure your hands are clean, and simply use your hands to blend all the ingredients thoroughly.
Loosely cover your bowl with a towel or paper towel and take a break for about ten minutes. Let the salt start to pull the liquid out of the cabbage, making the next step easier.
Using a sturdy wooden spoon (or a kraut pounder), pound the cabbage for at least ten minutes to allow the cabbage to break down and release the rest of its juices. You will see the consistency change and juices pooling in the bottom of the bowl.
Use your clean hands to pack the cabbage mixture tightly into the ½ gallon Mason jar. Remember, this recipe includes crushed red pepper, so don’t rub your eyes until you have washed your hands well.
Use the wooden spoon and pound the cabbage into the jar. Tamp it down as you layer it into the jar, ensuring no air pockets.
Pour any juice left in the bowl into the jar. Continue tamping the cabbage down to make sure it stays under the liquid level.
Use a large cabbage leaf or a weight to help keep the vegetable mixture tamped down and under the line of liquid.
Lastly, close the jar with a plastic Mason jar lid.
Let your curtido sit at room temperature on your kitchen counter for three days.
After three days, try a taste. If it’s sour enough and the flavors have blended, put it right into the refrigerator. Or use other cold storage methods, like a cool pantry, as long as the temperature stays under 55°F and above freezing.
If you want the curtido to have a more robust flavor, let it sit on the counter for another 24 hours before tasting it again.