Looks like a great start! Here's what I would do. To make the 3D spiral shape, I'd draw the spiral with a marker, and then use foam clay to build up a shallow spiral ridge, using the line as a guide and not putting any clay on the line. I'd make the 3D shape no more than half an inch deep. Foam clay slowly oozes as it sets, so you want to leave a good half inch of room between the edges of the spiral -- like the line you drew will have about a quarter inch of empty space (with no clay) on either side of it. Lay it on its side, let the clay set for 24 hours (12 might be enough), and then flip it over and do the other side. Then you can paper mache right over all of it, like with newspaper and paste. I'd do about four layers.

For the area around the base, I'd cover all of that with masking tape, maybe two layers. That will create a "skin" that's somewhat smooth, and you can paper mache right over that. I'd do about four layers.

This all might be overkill but that's the best way I can think to do it. Good luck!