Has it actually been explained how Barry Allen came back from the dead?

[Flash Gordon]

I was under the impression that he never actually died, and had been out running the Black Racer since the 80s?

Finally entering the fray against Darkseid in FINAL CRISIS.

[Captain Smith]

Glad the COIE simplified the DC Universe. Sorry, just had to say it. The real reason he came back - it was thought it would sell some books.

The best take on this was on Robot Chicken - where Batman said he was sick and tired of hero funerals. Everyone comes back through the magic amulet or time lines. He asked the crowd who had died - all of them.

[CentralPower]

Actually, "Convergence" would assume that Barry did not even come back....because he never died. (The closest thing to "clear" that "Convergence" got was that "Crisis on Infinite Earths" was prevented.)

You know what.... I dunno. We should probably know better than to try to makes sense of DC when they have given up.