What timber to use for formwork for concrete edging?

[ColinL]

Hi I'm trying to follow this video guide below to make a curved formwork for a new concrete edging in the garden but I'm struggling to find a soft timber (sheet?) that can be curved like the one in this video. The edging will be about 10 metres long. A basic timber will do as I'll probably recycle it after the border when completed, can anyone please link the product from Bunnings? Thank you.

https://www.bunnings.com.au/diy-advice/building-construction/cement-concrete/how-to-build-formwork

[ColinL]

That is a fantastic idea! Thank you very much for the advice! 

Cheers,

Colin