Buy some 3M Automotive double stick tape like this:
===AUTO PAK ATTACHMENT TAPE
Walmart and Target usually have it in stock.
Stick the Velcro to the 3M stuff and then stick the 3M stuff to your trim.
I've used it to fasten a pewter gargoyle to pretty much all of my vehicles for the last 17 years (yes the same gargoyle, I move it from vehicle to vehicle as I get rid of them).
I've fastened it to rough and smooth dash surfaces over the years and it never moves except when I take it off.