When installing the Rocky operating system, normally you can just select your system drive and let the installer to configure it automatically.
But in some occassions you may need to configure the boot partitions manually, for example if you had a system disk with a previous operating system installed that you need to remove to make space (if you have enough free space and you want to keep both OS installed then do not follow this procedure, just perform the default installation).
To configure the boot partitions manually:
Click on Select Installation, and select only the disk where you want linux installed. Make sure no other disk is selected.
Set the storage configuration as Custom, and press done.
In the next screen, select the "new mount points use the following partition scheme" Standard partition
If you are recycling a previous boot drive and you need to make space for the new OS, remove any existing partitions from the selected disk, just selecting them and pressing the minus "-" button, then confirm with the "delete it" button.
Then recreate the neccesary partitions by pressing the plus button "+". Example:
Select the /boot/efi option and set 1G for the capacity.
Press the plus button again and add a Swap partition with 32G.
And then, plus button again and add / leaving the desired capacity empty, so that the installation will use the remaining disk space for the root partition.
Press "Done" in the upper left corner, and accept changes.