Preheat the grill to medium and line a large roasting tray with a sheet of baking parchment (this isn’t essential but it helps keep the tray clean).
Scatter the vegetable chunks and lemon pieces in the tray and add the garlic. Tuck the thyme or rosemary sprigs slightly under the vegetables so the herbs don’t burn under the grill. Drizzle generously with a few tablespoons of olive oil and a few splashes of balsamic vinegar then season with salt, pepper and chilli flakes.
Grill for 10 minutes, remove the tray and gently toss the vegetables before returning the tray to the grill. Keep grilling for a further 10 minutes, or until most of the vegetables have taken on a decent amount of colour and are cooked through.
Remove from the grill and pick out the grilled lemon. Smoosh them into crusty bread and eat alongside the vegetable medley.
Serve immediately or leave to cool and serve as a side to any dish you like, such as the roasted sea bass.