Note - this is for lorax.

I partitioned the drive, but when I intended to proceed, the
installer told me I had no "/". So far, so good - I'd typed
"/root" for the intended root partition. When I deleted it,
all entries were red for "not enough space" and I couldn't
allocate space for "/" even though there should have been
enough. This lasted though deletion of all partitions, until
all were deleted - still no room to make a partition.
Reseting the partition table was a workaround.