For starters head over to https://apps4flip.com I am putting up a guide there on how to perform the actual installation of these apps.
I have heard rumors that there are people in certain communities who are charging to perform the service of installing apps like waze, whatsapp, etc on these flip phones. This thread is going to teach you how to do this for free!
I am going to document the process over time.
For now here is a sample app (zmanim - jewish times) that uses this hack to try out, this apk will install on all flip phones using the command 'adb install <name of downloaded zmanim apk>'
The file is attached to this post.
Enjoy zmanim on your flip phones!!
For all other question, apps, etc. Feel free to send me a pm.