The tutorial in your link is for vacuum veneering which is not the same as iron veneering. I'm not sure I see the need for veneer tape in the iron on method ( I could be wrong). I am fairly certain that the "buckle" method in my above post is standard procedure and serves to compress the joint. In that way when the veneer tries and pulls back the joint pulls back it does not open because there is extra material.
The best place for the joint is on the back or bottom.
Indeed you're right, I didn't read it thoroughly. I've only used iron-on method on edges and small areas without seams, so perhaps the buckle method is a better way. I use a similar strategy when making a seam in laminate countertop, although laminate is far more stable than raw veneer.
The basic problem, as I see it, is the cycling of moisture in and out of the veneer that the iron on method induces. I suppose once a person got accustomed to amount of shrinkage, it could be calculated into the "buckle" so to speak, but that's speculation on my part, I have very little experience with the method.
To the original poster; if you happen to have a few clamps, you could use the clamp and caul method, which has been around for centuries, and would be relatively easy on something this small. You could also just weight the sides one at a time. I can elaborate if you're interested.