Flaky: An unreliable person. A procrastinator. A careless or lazy person. Dishonest and doesn’t keep to their word.
A flaky Christian means you are unreliable in your Christianity. Christ can’t count on you to serve and the world can’t count on you to go out and preach the Gospel. You don’t care to serve and you end up being lazy. Christ didn’t flake out on you, so don’t flake out on Christ!!