"... I wanted to know exactly composition-wise where I needed to hide and how it all needed to happen because I wanted to capture the moment beautifully," Robert explained. "I wanted great photos."
The 15-year-old said the two planned out where Chandler, 22, would be kneeling and where Bindi would be.
"I sort of filled those shoes for the testing and thought, 'OK. I'll stand in,' get the blocking down," he said, adding that he "had the camera on a timer and got some pretty awesome shots of Chandler on one knee proposing to me."
Bindi announced her surprise engagement to Powell on social media in July by posting two photos of herself with her longtime boyfriend.
“On my birthday I said ‘yes’ & ‘forever’ to the love of my life,” Bindi captioned the images. “Chandler, close to 6 years ago I fell in love with you & every day since has been a whirlwind of adventure & true happiness. Here’s to a lifetime of friendship, purpose & unconditional love,” she concluded.
Just days after the big reveal, the conservationist and daughter of late animal expert Steve Irwin shared that Robert would be walking her down the aisle, assuming the duty that would have been her dad's.
"I think that for me, it'll be really important that Robert walks me down the aisle," Bindi told Entertainment Tonight at the time. "That's something that I really want to do.
"I'm always so grateful that Robert is there, and he has been such a big part of my life and he's always stepped up and been the one to give me a hug when I need it and encourage me forward in life," she continued. "So he will definitely be the one to walk me down the aisle when the time comes, and I think that will make it really special."
"And I think that's what dad would have wanted as well," Bindi noted.
Bindi and Chandler are set to tie the knot next year.