This LiveScience article suggests the areas aren't major:
The scant areas that are free of snow and ice make up less than 0.4
percent of the continental land mass. In places there, the wind has
built sand dunes.
This article by Burton-Johnson et al., 2016 on automated satellite analysis methods, summarized in this DailyMail article, indicates refined estimates nearer 0.18% of the continent is not covered by ice/snow.
Based upon the area of Antarctica from Wikipedia (you might be surprised how big Antarctica is!), that would equate to around 10,000 mi$^2$ of uncovered land (see comments for comparison). Of course it may well be that not even all of that area is sand.
It looks from the articles like the largest place to find these sands are the McMurdo Dry Valleys, such as Victoria Valley, which are on the Eastern Antarctica sublandmass [see the sentences directly above the image entitled Deglaciated Antarctic Toporgraph, plus that image itself].
So it sounds like they really do exist, but are relatively rare expanses!