hello, i think the best option is to make the partitions from windows, 512M at least, then in solus live mode, use gparted and format in fat32, and flag it as efi and boot, then proceed with the instalation as normall.
It's important to have partitions ready before installation, as the solus installer don't do it automatically.
In a nutshell, make the partitioning from windows, one at least 512MB for EFI partition and then one for /
, the size depends on what you need, after doing that you can continue to the installation of solus.
I hope it helps.