Herbes de Provence is a mixture of dried herbs commonly used in the south of France. You can find commercial mixtures in specialty stores, but it is easy to make your own. Mix 1 tablespoon each (or equal proportions) dried thyme, rosemary, oregano, marjoram and savory in a small jar. If desired, add a pinch of dried lavender and crushed aniseed.
Call ahead to your fish market to have a fish, whole prepared for you. Ask the fishmonger to clean the fish--gutted, gills and scales removed, butterflied with backbone and rib bones removed--but leave the head and tail intact. This preparation makes for an impressive presentation at the table, but it's easy to work with.
Variation: To roast the fish in a foil packet instead of a salt crust, place a piece of foil (a little more than twice the length of the fish) on a rimmed baking sheet. Brush 1 tablespoon oil over an area about as big as the fish. Place the fish on the oiled foil. Season and stuff the fish (see Step 3). Close the fish and fold the foil over it; crimp the edges to seal. Roast the fish, 20 to 30 minutes (8 to 10 minutes per inch of thickness). Remove from the oven, open it up and gently scrape off the herbs and lemon slices. Use an offset spatula to remove the top fillet; transfer to a warmed serving plate. Lift away the bottom fillet and place on the plate. Finish with Step 5.