It's possible to embed an Excel file within a PowerPoint slide by highlighting the Excel table or sheet you'd like to embed > Copy > in PPT, Home tab > Paste > Paste Special > Paste Link button > Microsoft Excel Worksheet Object
If the Excel file is stored in Box though, this results in various errors if you try to update the link within PowerPoint. Close out of the Excel fie, go to the Powerpoint, double-cick the Excel table/worksheet within PPT or right-click it and choose Update Link results in the following errors:
"The server application, source file, or item can't be found, or returned an unknown error. You may need to reinstall the server application."
"The linked file was unavailable and can't be updated."
- In order to work-around this issue, we have found that you can insert the 'Edit Links to Files' button in the PPT toolbar and redirect the links to C:\Box instead of the default https://api.box.com/wopi/files