Instead of placing the vertical framing members square on the frame just angle them to 22.5 degrees where they meet. Not 45 degrees. Then you only have to miter the top and bottom plates.

Op says, "I have no hardware to do that. Any other way?" Hire someone.

is it still r/DIY ?

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Triangle wood molding/trim can be ordered. Might find one fits your other board width.

No. Anyway table saw is required because it is going to 6 ft tall. Like u/ok46reddit advice for now.

You can rent a circular saw or a table saw from the hardware shop for pretty cheap ... and if you don't want to, a basic saw and miter box are pretty inexpensive as well.

Otherwise, triangle molding would work to a degree, like another comment said.

You can use a circular saw to do a 6’ mitred cut no problems. If you’re not confident you can keep it straight you can clamp another bit of wood on to use as a guide. Obviously moot if you don’t have a circular saw, but if investing in a useful tool is an option, that’d be a cheapish way to do it.

And as others have said, 22.5°

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To make it beautiful, you can simply fill the gaps with a sealant of the desired color.

I mean how far does it go? When you use a saw, is it not DIY if you didn't build the saw?

This is definitely the answer. Unless it’s a pet fish, the enclosure probably doesn’t actually need to be seamless.

Do henges and add blocks near the hinges on the inside to keep the screen from collapsing completely.

Also, if you use blocks on the inside (opposite of the arrows in illustration 4) they can be a lot bigger than you’d want on the outside.