Preheat oven to 325°. Cut a sheet of 18-in.-wide heavy-duty foil three times as long as salmon and center it on a rimmed baking sheet, letting ends hang over. Set salmon, skin side down, on foil. Sprinkle fish evenly with orange zest, shallot, and fennel bulb. Bring corners and sides of foil up around salmon to make a canoe with 2-in. sides.
Pour orange juice into a glass measuring cup and add vermouth to make 3/4 cup. Microwave until steaming (about 170°) and pour evenly over fish. Drizzle with 1 tbsp. oil and sprinkle evenly with 1/2 tsp. salt, the pepper, coriander, and juniper berries. Tightly roll ends and sides of foil together to create a pouch.
Bake salmon until cooked through three-quarters of the way from edge to center of thickest part (which will still look wet; open foil and cut fish to check), 12 to 25 minutes, depending on thickness.
Slide two long metal spatulas under fish and carefully transfer to a long platter (Murray likes to use a madeleine pan), leaving poaching liquid behind. Sprinkle radishes, about 1/2 tsp. salt, and remaining 1 tbsp. oil over fish. Scatter torn fennel fronds on top. Serve with Dill Crème.
*Ask a fishmonger to remove bones, or do it yourself, using fish tweezers or pliers.
Make ahead: Through step 3, up to 1 day, chilled; bring to room temperature.