DIY enthusiasts needed - help me make this chair

[YellowPants9]

I want to make this chair. I'm very handy & the upholstery's no problem. My issue is with the design of the frame (which I intend to make in ply). The 'petals' lean outwards in a semi-circle so will need some sort of strapping to hold them securely while they have the pressure of a person leaning against them. I wondered about using car seat belt ribbon as it's incredibly strong but thin & has the bonus of being flat. I can put glue & metal brackets between each petal. But can anyone else think of a better idea? I'd love to see one of these stripped back but couldn't find anything similar surfing the net. Also I need to find a way of securing each petal at the base? A biro drawing would do if you can think of a cunning plan.. Many thanks in advance..

The photo you've listed looks as though it may have a sort of rigid 'cup' around the outside , i.e. the petals are only really on the inside but have the illusion of being solid if that makes sense?

It looks as though they've been built up and shaped with the foam as the outside back looks flat. Might just be me though!

this video shows someone re-upholstering a similar chair

Two more pics to show the sloping angle of the outside edge.

Your final picture shows perfectly that they are not separate petals but shaped part of an inverted cone. Practice with cardboard!