From time to time you might need to create partitions manually in order to install Ubuntu on a specific hard drive in a multi-drive PC.

Get started by deleting all partitions on a specific drive

Next, create a new partition with size 537 Mb:

Format with EFI System

Next, create a new partition with the desired size:

Format with Ext 4 and select mount point as /

Finally,

Install Ubuntu by selecting the root hard disk /dev/sda or /dev/sdb