Fresh from his sacking as Ajax head coach, Heitinga returns to England after spending the past two seasons coaching at Everton and Liverpool.
Ahead of this weekend's trip to West Ham, Frank said: "It was a process we did together.
"Of course I was a big part of it. I think he was a standout candidate with everything he's experienced. A top playing career, that's one thing, but also I like how he then did after that in terms of his experience in the academy of Ajax. So he walked the hard way.
"He's also been trying to stand out there where there's a bit more noise and wind sometimes. That gave him a perfect profile. I'd met him now a few times before, and all the character references we took, just a top guy, top integrity, top football person."