Manjaro ARM for Pinebook

[tophneal]

So download the image, flash it to micro SD, flash it to USB, start from SD, have the SD set up, reboot and then dd if=/dev/usbsomething of=/path_to_eMMC ? What about uBoot?

Don't flash the USB, just copy the .img to it, so you can write that to the eMMC. Otherwise, yes. No need to worry about uboot. Those img files are pretty self contained, they hold uboot at the appropriate location already, which will be written to your drive when you run dd.