Qubes OS Install on a 1TB SSD USB. Best configuration for two separate partitions (installation + Storage)?

I tried to do a custom install to achieve the following configuration


The settings take up the mount points for /, /boot/efi, /boot and swap. As soon as I reach the ext4 300GiB vm-pool entry, it demands a mount point. When I choose /var or /home to set it temporarily, it just freezes. I need to segregate the remaining volume into vm-pool and an extra storage partition as mentioned in the OP.

What should I do now?
Try partitioning from an alternative OS and directly select the partitions? How do I create the Volume groups then?
Thanks.

Edit:
Just figured out. Blivet Gui.

Issue:
No options for setting mount point for root/swap
Also, options like LVM thin provisioning, standard partition etc are not the same. In Blivet device types are “Partition, LVM2 Volume Group, Btrfs Volume” only.
Setting mount point is available only for Btrfs volume and not for LVM2 Volume Group.
Blivet throws error for not setting mount points for root and swap, but doesn’t provide option to set it.
What am I missing? Should I go through commandline?