Slice cabbage into thin strips and place in a large freezer bag. Roll out all the air while sealing, then place in the freezer for several hours, or overnight. I generally keep a bag of sliced cabbage in the freezer at all times in case of side-dish emergencies.
Preheat the oven to 375 F and line a baking tray with parchment paper
Dump frozen shredded cabbage onto baking tray, drizzle with olive oil, season with salt and toss to combine. Spread out into a thin, even layer and place in the oven.
Roast for ~30 minutes, checking frequently and stirring the cabbage around as needed. Some of the thinner slices will get extra caramelised and crispy, which makes this dish even more delicious!