I am going up to Disappointment in about a week and a half, so I was testing out my hammock last night in the yard. I was nice and toasty for the most part, except for my feet about half way through the night. I've had this problem before and I'm thinking it's because my feet are elevated and losing blood flow.
Does anyone else the problem of their feet getting cold, and what solutions have you come up with?

Down footies or booties. Wool socks. Some put a foot mat that adds insulation at foot end of their hammock.

What setup are you hanging with?

Goose feet down booties are the ticket!

I had on wool sock, wrapped in flannel and in the sleeping bag. The temp only got down to about 45°, so I thought that'd be enough.

I'm getting a pair of down booties. Thanks for your suggestions

+1 on booties and wool.
Some other thoughts:
Make sure your feet are dry. Feet that are too hot sweat and wet out some of the insulation and lead to mid-night cold feet.
Make sure the socks are not too tight.
If needed place your coat around you feet to help insulate.
For real cold nights a “hot hand” toe warmer goes a long way.
Maybe change your hang angle or how you lay to lower your feet a bit.

I have a pair of Enlightened Equipment Torid Booties (used to be called 'Sidekicks') that are fantastic. They're made out of synthetic Apex insulation so if your feet sweat a bit they'll retain insulating properties. You can also select what insulation weight you'd like depending on what temps you expect to see and how cold your feet run. Plus, they're made in MN.

EE Torid/Sidekick Booties