Preheat the oven to 250°F.
Prepare the vegetables. Peel and thinly slice the carrot. Slice the green onions and yellow onion. Rinse the cabbage leaves, pat them dry, and tear them into smaller pieces.
Place the prepared vegetables on a baking sheet. Spread them into as close to a single layer as possible so the moisture can escape during roasting.
Drizzle the olive oil over the vegetables.
Sprinkle the sea salt evenly over the vegetables.
Gently toss the vegetables with clean hands or utensils until the olive oil and salt are distributed throughout.
Spread the vegetables back into a single layer.
Roast at 250°F for 1 hour and 20 minutes.
Begin checking the vegetables during the final 15 to 20 minutes. Smaller pieces may become crisp before larger pieces. Remove any pieces that are finished early if needed.
The veggie chips are ready when the vegetables have noticeably reduced in size, the surfaces look dry, and the edges are browned or crisp.
Remove from the oven and allow the vegetables to cool on the baking sheet for several minutes. The pieces will firm up as they cool.
Serve once cooled to your preferred texture.
