Sit adverbs are provided in this article. The words listed here are commonly found along with the verb sit in sentences. This reference page helps answer the question what are some adverbs that describe or modify the verb SIT.
absolutely, actually, awkwardly, barely, calmly, closely, comfortably, commonly, contentedly, daily, deliberately
directly, easily, finally, firmly, frequently, generally, gladly, gracefully, habitually, happily, hardly
heavily, helplessly, humbly, idly, immediately, lightly, literally, loosely, meekly, merely, mostly
nicely, normally, occasionally, passively, patiently, peacefully, perfectly, permanently, possibly, probably, properly
proudly, quietly, rarely, really, safely, scarcely, securely, separately, silently, simply, slowly
squarely, suddenly, supinely, tamely, typically, uncomfortably, uneasily, usually, willingly
Hope this word list had the sit adverb you were looking for. In addition to adverbs used with sit, other example verb adverb pairings can be found on this site.
You can help by adding more adverbs in the comments. Thanks.