Install GRUB modules for BIOS and EFI:
yum install grub2-pc-modules grub2-efi-x64-modules
Install xorriso and mtools rpms that are used by grub2-mkrescue while creating the ISO image:
yum install xorriso mtools
Generate a bootable ISO image using the command:
grub2-mkrescue -o cdrom.iso [source_directory]
An ISO image cdrom.iso of about 13 MB in size should be sitting in your working directory now.