How to properly make bios grub boot area on gpt disk?

Question

GRUB

I connected a gpt disk to the old computer and installed it in one of the (nine) debian 8.4 partitions using the standard pseudo-graphical installer. Now it is loaded (albeit buggy every other time) not only a fresh installation, but also a couple of Linux from other partitions that used to run on uefi. I want to learn how to do like this installer, only manually and without glitches))

Answer 1

PS: By uefi, the disk worked on a modern laptop.

Answer 2

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