Preheat oven to 250C.
Wipe each flounder dry with a tea towel.
Place the flounders on a large baking tray, darker skin side up.
Scatter over herbs and garlic, drizzle generously with olive oil and season with salt to taste.
Roast the flounders for 10-15 minutes or until the flesh is just cooked through (check the neck: the flesh should come away easily from the bones)
Heat a frying pan on high until smoking and cook the lemon slices until blackened.
Arrange the cooked lemon slices over the flounders and serve immediately.