Assembly checkbox

Hi!

I need a checkbox that gives the option to the customer if they want us to do the assembly or if they want to do it themselves.

So let’s say that I have in mind a checkbox asking if they want us to assemble the product, and it needs a description (Place needs to be pre-prepared). I also need it to show up in cart (let’s say: Assembly – 170€)

I made custom single product pages, so what would be the best way to do that?

Thank you

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