In a food processor, combine the lemon zest and juice, the picked thyme, bay leaves and garlic and pulse until it becomes a coarse paste. Add the egg whites and puree until very frothy and foamy.
In a large bowl combine the herb-egg white mixture with the salt and mix until it becomes a moist paste.
Place half of the lemon slices and whole thyme in the cavity of each of the fish. On a baking sheet, place a little less than half of the salt mixture in two rows. Lay the fish on top of each row. Pack the remaining salt mixture around the fish to completely encase them, pressing the mixture firmly on the fish to create a crust.
Roast the fish for 25 minutes. Remove and let rest for 10 minutes.
Crack open the salt crust and brush the excess salt from the fish. Remove the top fillet, pull the spine out and remove the bottom fillet. Drizzle with olive oil and serve.