It kind of sounds like all you want to make is a beet terrine. I'd say skip making the borscht unless this is a way to make use of leftovers.
You can just skip this if you know how to make a terrine.
Instead just roast the beets, thinly slice
Then layer in a loaf pan line with plastic wrap. You can alternate other things in the layers, like sour cream or maybe pickled onions.
Once you get to the top fold the plastic wrap over the top, place in fridge, and weight with a couple heavy cans or a brick for a few days.
Remove, slice, eat.