Cover the bottom of a roasting pan with a layer of kosher salt. Lay out a few thyme sprigs and then place the beets on top. Cover with foil and roast in the oven at 350 for 30 to 45 minutes.
To check the beets, get a toothpick and insert into the beet. If it goes in easily, they are done. Let them cool until you can hold them comfortably and then peel off the skin. The beets are easy to peel when warm.
When beets are cleaned, cut into bite-size pieces and mix with chopped thyme, diced shallots, orange oil and tangerine juice.
For the raw beets held aside, make sure they are free from dirt and slice paper-thin on a mandolin or slicer width-wise. These beet disks will be a garnish, and you can do them ahead of time and keep them in clean water until ready for use.
For assembly, place a few pieces of watercress on a serving plate and put the marinated beets on top. Scatter the tangerine segments, goat cheese and pistachios and drizzle with the basil oil and a bit of the beet marinade. Sprinkle on the basil and place the beet disks on top.