You can use a pastemask checkerboard pattern to apply paste on the square, with the pattern covering your via in the middle. Then you shouldn't have a problem with wicking into the via as long as it's surrounded by soldermask (you will need to add this to your padstack.)
More here: https://www.pcblibraries.com/forum/ipc7093a-btc-qfn-solder-mask-defined-thermal-pad_topic2154.html
You can also cap the via, at some extra cost.