I’ve seen a few standing up guitar cakes, you should be able to use the same method, I know versus a walker and Jessica Harris have both done one. You use a piece of mdf or something similar and cut it the shape you want your cake to be (so you’d cut a number 1), obviously you need to dowel it well and have a strong, stable base board but the support on the back of the cake helps it stay stood upright, you should be able to find a tutorial online, I’ll have a look and see if I can find the ones I mentioned once I’ve put little man to bed.
