I applied in late december, was called in mid january for a phone interview that I passed, but I didnt have my passport yet so I wait until i received it. I emailed them a copy of my passport and was contacted for an interview on March 3rd.
They flew me to Denver on the 2nd, paid for the flight and hotel, and the hotel was walking distance from the place of the interview.
There were about 30 of us there. It started with a presentation about Frontier and then we had something like a Q&A session with one of the flight attendants. We were called out one by one for interviews, first with current flight attendants and then with inflight supervisors. They were all very welcoming and made me feel really relaxed. Almost every question they asked me can be found on glassdoor, and I also read a prompt for them aloud.
Lunch was provided. Afterwards its just a waiting game to find out if you were offered a job. If youre lucky, you'll be interviewed in the morning and you'll know if they picked you by early afternoon. Otherwise you'll be waiting in their cafeteria all day.
Some of the other reviews recommended "working the room" since the flight attendants would be watching you. Personally, I stayed in my seat and conversed with those around me. I'd just recommend being friendly and easy to make conversation.
After being offered the job you fill out some forms, get fingerprinted and drug tested, and then you can head home (or back to the airport for your light in my case).