Complex sentence: Slessor, who became well known as a modernist poet, knews and admired McCuaig, loved his expression and thought he was a marvellous technician according to Dutton.
Split into simpler sentences: Slessor, who became well known as a modernist poet, admired McCuaig. Slessor "loved his expression" and "thought he was a marvellous technician" according to Dutton.