Hello,
This should be possible by doing the following:
1. Click on the iFlash menu and select Preferences.
2. Go to the Advanced tab and choose "Edit New Deck Template".
3. Edit the deck template however you'd like and save.
HOWEVER, this is currently broken in iFlash 2.9.3! I'll fix it in the next bug update (2.9.4) which should be coming soon.
Thanks!
Davey