/3/ - 3DCG

>>570645
I used inset (i) several times on a plane. Then I turned on proportional editing (o) with sharp mode selected (experiment with the others) and moved the innermost plane upwards and added a subsurf modifier. Make sure proportional editing is turned off with O. Next I added two edge loops with ctrl+r and scrolling up once, scaled them along the x axis. Repeated for two more with the y axis. Add a support loop (in pink) on the last section before the top. Can't remember if I inset the top or not but after that it's all about editing edgeloops (g-g) and adjusting subdivision levels to get the shapes you want.

I included the picture for illustration, the final was completed before I thought to do the example images.

Good stuff on topology.
https://www.youtube.com/watch?v=UFL24N8G8ow&index=17&list=PLxt9ZAGPLIpeB8TcHrpzxvEI4Ve3SfZBC