The Lord Of The Rings actor, who is currently starring in Carnival Row, and Miranda were married for three years before they called it quits in 2013.
But they have remained friends to co-parent their 8-year-old son Flynn, with Miranda also getting close to Katy.
Orlando also opened up about his proposal to the Roar singer on Valentine's Day this year.
"To be honest, she loves a theme as you can see in everything she does. She loves a big moment," he said, speaking about his decision to pop the question during an intimate helicopter ride.
“I’m still trying to get her to wrestle into the small moments,.
"The cool thing about what we’re doing — we’re learning to do the small together. I think we’re both fully aware that it’s a mountain to climb and that that mountain won’t stop, in terms of a relationship, because I think that’s what it is. And I love to evolve and fortunately, she does too.”