@Stephanie Postma - As far as I know, this is still not possible using out-of-the-box Miro functionality. There is even a wish list post requesting this functionality - I suggest you upvote it:

https://community.miro.com/wish-list-32/create-individual-frames-from-selected-objects-4814

Miro Developer Platform

This likely could be accomplished using Miro’s developer SDK. You--or someone with a development background--could review developer platform documentation to see if this is possible and what the effort would be to create a custom web-plugin to do what you are asking