Cheating with my ex - How to initiate it?

I made a post earlier about cheating on my current GF with my ex.

We’re both with other people now, but my current gf is quite vanilla in bed and can’t really fuck for more than 10 minutes before she gets sore, and my ex was incredible in bed. Found out yesterday from a mutual friend that my ex still thinks of me every day and would drop her new man if I text her.

I don’t want her to drop her current boyfriend because I can’t really break up with my girlfriend at the moment so that could get messy, but I do want to meet up with her and fuck her again which it sounds like she’d be down for. When they first got together she told me he wasn’t as good in bed as I was (smaller, a bit boring, sometimes came too quick), but eventually she stopped texting me so I assumed things got better. Apparently not.

What’s the best way to approach this and try to suggest a FWB type situation? We don’t have each other on social media anymore, seems like I’ve got the go ahead to contact her but obviously want to keep it discrete.