I always assumed that PD negotiated the voltage and current via a protocol using a controller.
I’d be glad if this could be solved with two resistors, as you mention here. Can you give us more information?
73, Peter - HB9PJT
“Google Search resistors” will give you plenty to read. The Hackaday article looks good to start with. I should have a full USB spec somewhere at work. I’ll go searching and “back it up” for when I retire 
But the device needs power to do this!
As USB C has the same connector at both ends of a cable a device cannot output power until it knows what it is connected to. The source has pull-up resistors and the sink has pull-down resistors. Different resistor values give different ratios and so the source can advertise up to 3A of 5V are available.
Anything other than 5V or beyond 15W will need some negotiation via the protocol.
Thank you for your excellent suggestions. https://hackaday.com/2023/01/04/all-about-usb-c-resistors-and-emarkers/
73, Peter - HB9PJT