Allow the glue to set a little bit and very carefully pull up the assembled piece and remove the sticky tack underneath if it is stuck to it, or just move it over and away if it isn't. Now very carefully push down on the square dowel against the base to "straighten" everything up so the square dowel is what is most in contact with the base. Rearrange any of the palisade spikes which may have been moved askew. Allow it to cure.

Select how far back you want to place the palisade on the base. Make sure it is at least a little bit back from the very front edge so you can cover the bottom of the spikes in texture paste like seen in the first picture. other than that consideration it is personal preference or whatever is practical for you.

Lay a thick line of superglue down the bottom of the squared dowel and place it on the the base. Let it dry for a minute or two.