the 10" opening is too big for my printer, I limit out around 8". I have done some stuff with Tinkercad, it's not too bad but it probably feels like using paint if you've ever used a bigger CAD program. I'd probably create the spout portion first, then cone your funnel portion to shape. Probably the hardest part is getting the hollowed out pieces centered.I need to print a funnel. 2.5" small opening to about 10". I haven't looked hard enough for one on the webs and I don't want to cad it either... That is the problem with 3d printers for people without cad design skills.
I don't know anything about design for 3D printing but I can easily put a model together for you. I have lots of experience with Solidworks and Inventor (what I currently have access to through work).I've played with tinkercad a bit, as well as Fusion and some of the other offerings. I'm just not good because I haven't used any of them. Full disclosure I bought a funnel but it arrived cracked and was really flimsy and so I decided I needed to not be a doofus and just print what I need. My print parameters are 11x11x9.8.
I'll find what I need this morning on thingiverse.