The way I think it works(though I'm not 100% sure):
1. Buyer buys an item, sends bitcoin to the address handled and displayed by Selly/Shoppy
2. Once Selly/Shoppy receives the coins, the coins automatically get sent to your provided address minus the cutoff percentage
Did I answer your question? Or are you asking literally how to do it technically? Because I'd suggest hiring a software engineer for that.
First thank you for the kind reply!
Yes I understood how they works!
The problem is I need to know what's the best way to accept bitcoin payments in such cases.
Due to business model ( my cutoff fees will be just cents so i can't pay any other payment gateway to manage payment gateways? )
So if you can please help me what's the best way to accept bitcoin payment in this scenario