The tutorial I used for reference is this one. It's in German but the pictures are enough to go on.
The felt soil nicely wedges in the flower pot so I haven't needed to glue it in place yet. I picked up the pot from the Scrap Store. I may re-paint it at some point but for now I quite like the scratched up gold look.
With my felt cactus complete all that's left to do is add my pins and start a new sewing project!