I am 5'1" and the dress hits me right at the top of my knees. It looks great alone or paired with a jean jacket or cardigan. I also like adding a lightweight scarf for some extra color if I don't feel like wearing a statement necklace.
At the moment my favorite thing to wear under these dresses are the Old Navy Go-Dry High Rise Side-Pocket Compression Shorts. I never know what kind of day work might and I enjoy the comfort of not worrying about flashing anyone and these have a slight Spanx-like ability to keep things smooth. To be honest I didn't notice the pockets until I was looking up the shorts on ShopStyle Collective to post here! I might utilize the pockets at the gym but definitely not under a dress.
Last but not least, if you haven't signed up for Ebates - you should (and can do so here)! They offer cash back for many online retailers but they have also have an "In-Store Cashback" option. Often Old Navy is listed as an in-store option and then I can earn cash back if I pay with my connected card (you can link almost any credit/debit card to your Ebates account).
Please note this post is not sponsored by Old Navy or Ebates - I am just a fan of both brands!