Twin Bose L1 positioning onstage.

We use our line arrays as monitors behind us, can adjust volume as needed for band members. We use powered 15” speakers off to the sides so we don’t get blasted but it’s not so loud to kill the audience either.
 
Comes as a pair - do you mean the Blackstar Fly 3 Bass? Are you aware how small they are? I suppose you could try putting them on mic stands as close up and personal monitors, but I would have grave doubts about how useful they would be on a live stage. I was thinking more in terms of their Unity range.
I use tiny Blackstars all the time. They do what they need to . But we are on a 10 day tour around Holland at the moment and have found that staggering the Boses on the stage works brilliantly. One goes stage left rear, the other in front of me, angled to transect. We can all hear what we need and the audience is getting a good balance because the sound sits out front back and controls remotely from there. Happy days! Thank you for info though.