I've made two for my Death Guard (3 if you count one that's carrying my
GUO) and the core construction is generally the same. Couple of Nurgling bases with the top ones chopped off to level it out then actual model bases to make the Palanquin's core itself.
This one is made specifically from an upturned 32mm base and 6 Cybermen bases from Warlord's Doctor Who game to form the shape of Nurgle's rune.
This one is made from 2 40mm square bases and 2 cavalry bases as its core with various chaos bits and green stuff added on top.