Hey, we have backed you on this. You can definitely set a background voice-over audio to your slides. Follow below steps to do it.
Step 1: Make sure you are inside your Interactive Deck Editor.
Step 2: Go to the tools tab and from ‘Deck Settings’ section, enable voice overs.
Step 3: Now check that in your slide creation form, a new section has been added, called as “Voiceover”
Step 4: You can now upload your voiceover media files for each slide via this section.