How to delete all partitions from iMac without an OS installed and rebuild a fusion drive without UUID

a friend of mine bought a second hand iMac and they erased sort of everything from the iMac before it was given to him. There is no OS installed and it's not possible to instal a new version from OSX from Internet Recovery because the Hard Drive is greyed out. When I open terminal and check distil list this shows up: What are those 17 disks? and how can I remove them and rebuild the whole harddrive? Everywhere I look they say that is should have an UUID but when I use diskutil cs list it says "No CoreStorage logical volume groups found". iMac 27" early 2016 2TB Fusion 8GB Ram Internet recovery (El Capitan) I hope there is someone that can help me! So this is actually my question. Can I delete everything there is on this harddrive and rebuild it al? grts, Alex