Copying boot files to USB

First run in terminal

diskutil list

Take note of the other partition identifier of the USB (the partition where macOS is not installed). Let's mount it to copy the necessary files.

sudo diskutil mount /dev/diskNsM

Replace the N and M with the corresponding disk indentifier obtained previously. With the partition mounted, create the folder EFI in the root of the partition and inside EFI, copy the OC and BOOT folder

Manually create a boot entry

The UEFI that ships with the laptop allows creation of simple boot entries, as we do not need to append any boot arguments like when booting a Linux kernel directly, manually browse the partitions and point the boot entry to OpenCore.efi found in the OC folder.