Print one of each (my settings are below). Then place the spadix inside the flower flat side down and push the bumps through the hole in the bottom of the flower until it stops. Then align the bumps on the spadix with the bumps on the top of the stem and snap them together. You may wish to add glue for a sturdier more permanent assembly. 

If the stem is too tight you can play with the scale of the parts until you get a nice tight fit for your machine.

Below are my print settings:

Flower: 

• Spiral vase mode
• top layers: 0
• bottom layers: 4
• extrusion width: 0.6 (for sturdier model)
• brim: 'Outer brim only',  5mm width

Spadix: 

• Spiral vase mode
• top layers: 0
• bottom layers: 4
• extrusion width: 0.6 (for sturdier model)
• brim: 'Outer brim only',  5mm width

Stem: 

• Spiral vase mode
• top layers: 0
• bottom layers: 0 (zero bottom layers is important for snapping the flower together)
• extrusion width: 0.6 (for sturdier model)
• brim: 'Outer brim only',  5mm width