Don’t go crazy, but dekay has a reasonable idea. When actually leveling a floor, you have to know what your are doing, and do it fractions at a time, for a variety of reasons. All you want to do is reinforce, stabilize, and provide support at the joists along the area where your turntable is. Thus, if you use a jack, I would not raise the area more than a 1/4”, put a couple 2x4’s, or perhaps get some treated 4x4’s, stand them in place (on a 12x12 concrete block as a ‘footer’) and lower the joists back down upon the vertical 4x4 with the jack. Pretty easy actually, but depending how much crawl height you have, can be cramped, so scope everything out, precut the lumber, etc. There is no real need to make full height pilasters out of block for what you are doing and trying to achieve, that would be overkill.