How do you ask your ex to hang out with you?

When you split up with someone (even if the split-up was a friendly one) it's simply time to move on. The reason for this is you have had an intimate relationship and some fond memories and perhaps not so many fond memories. Still, one of the two is still in love with the other (sounds like you are.) It's mentally healthier to move on and spend more time with friends until you meet someone else. Try not living in the past, but reach for the future.