Never seen Flexi, so I can't help, but from the laser standpoint, it doesn't care where it comes from, it just has to come in as a "printed" document. Can you print from Flexi or is do you "send" it to a device?
If you print, I'm not sure why it wouldn't work. Can you print to a PDF from flexi? If so, you should be able to print from the pdf to the laser.
Basically, if you can print from it to your desktop printer, then the laser should take it fine.
For those with Flexi, and flexi with a laser, what's the issue with it that causes it not to work? (I'm just curious, as I've not seen that question before).