For the salmon:

Preheat the oven to 275°F. Pat the salmon fillets dry with a paper towel. Brush both sides of each fillet with the olive oil, then sprinkle both sides with salt. Divide the thyme sprigs into 8 equal portions, then arrange the portions in mounds on a half sheet pan. Top each thyme “nest” with 1 lemon slice and a salmon fillet. Cover the pan loosely with parchment paper. Roast the salmon for 12 to 15 minutes, until an instant-read thermometer inserted into the thickest part of a fillet registers 118°F for medium-rare. The salmon should be just cooked through and soft when pressed with a fingertip. Let rest for 3 minutes before serving.

For the green goddess dressing:

In a blender, combine the garlic, shallot, anchovy, parsley, basil, tarragon, dill, chives, green onion, mayonnaise, yogurt, avocado, and verjus and process until smooth. Season with kosher salt and pepper. You should have about 11/2 cups. Transfer to an airtight container and refrigerate until ready to use. It will keep for up to 2 days. To serve: Trim the vegetables as needed and arrange on a platter or large serving board. Transfer the dressing to a serving bowl. Put the sel gris into a small pinch bowl. Serve the vegetables with the dressing and sel gris alongside.