How to change grub-efi timeout with live-build?

I need to automatically boot the live Debian system created with live-build, however the default grub timeout is set such that user interaction is required to boot. I need to change the timeout but am coming up short on finding information how to actually do this (Information on live-build seems to be quite scarce). I’m using grub-efi by adding --bootloaders "grub-efi" to lb config.

I’ve seen this question which prompted me to try storing grub.cfg in includes.chroot_after_packages/boot/grub/ but that didn’t seem to have any effect. Adding grub.cfg to bootloaders/ had the effect of cancelling out the default grub. I’ve seen that in \usr\share\live\build\bootloaders on the builder system are some bootloader configs, but grub-efi is not present.

How can the timeout be changed to allow an auto boot? Thanks