To flip the disk in the Apple II version: press F5.
When asked in the game to enter the slot for voice output press 0 or the game will hang.

Use the Apple II Type N Talk version for voice output.
To flip the disk in this version: press Tab, choose File Manager, floppydisk1,
select the desired side, hit Enter twice, then Tab again to close the menu.
When the game asks you for the speech slot, answer 2.

To flip the disk in the Atari 8bit version: File -> Attach Disk -> Rotate Down