I'd like to apply a decal that spreads over all faces of a box cover.
In order to to this I'm replacing straight faces and fillets of the box with surfaces.
I've extracted some curves and turned them to splines witg fit spline command.
I've tried various commands, and the one that seems to be quicker is boundary surface. The problem is that it won't generate the surface because it will create some spikes which will make the surface self intersecting:
I'm attaching the file. Do you have any pieces of advice in order to make this a unique surface ?