I want to make semi 3d dinosaurs like these. Could they be made in advance and dried on a curve or is it better to make them directly on the cake? Also is there any problems with such a large amount of fondant stuck to the side of the cake? Do they need some support? I’m worried they might pull off the cake .
sure they could be made in advance like you said -- if it's a fondant covered cake it's easy to stick it one with melted choco or piping gel -- if it's a buttercream covered cake then I would slant them into the cake on a blob of icing -- so they wouldn't be as prone to drop off -- should be fine --
but if you wanted more insurance you could slide a skewer or a straw into the back of the object on the diagonal and let it dry as the dinosaur dries and then use that to adhere it too -- either so it slides down into the cake or goes in sideways at a diagonal -- they are kinda thick --
I would definitely make them in advance and let them dry for a couple of days. There shouldn't be any trouble with them sticking onto the side of a fondant cake - use melted chocolate for a super strong bond. If the cake is buttercream, I would just use an extra blob of buttercream to stick them in place, as -K8memphis said. You can get the same effect without making them quite so thick. The key is rounding off the outside edges, which makes them look 3D.