Note how the strips of pellon interliner, when cut on the bias into strips, can easily follow curves.
The very fine but open weave is very easy to drape over the corrugations at the cone flange.
Then a small bristle brush is used to work out any air bubbles and excess veneer glue.

Remember all that Scotch tape on the cone?  I found that brushing lacquer thinner or acetone around the edges of the tape will cause it to release almost instantly without the adhesive soaking into the paper and it does not damage the wood glue you used on the other side of the cone at all.
After the veneer glue is dry, you can drop the cone back into the speaker basket and clamp the flange.

Now is the time to apply Permatex brand flowable silicone windshield and glass sealant Part #  81730 to the corrugations at the flange. (Available at most auto parts stores.)

This sealant will soak part way into the paper before setting up thus helping to consolodate the damaged paper fibers and still provide flexibility that another layer of the pellon on this side would not provide.
The silicone will look very wet and glossy.  As the silicone cures, go around with a dry bristle brush and lightly scuff the surface to tone down the gloss.