Need ideas for walled off 18s

[Dagwoodjf]

I'm new to this forum. I've done a few builds but never a Walled off build. I have a few questions really

1--when building a sub wall, do you simply build the skeleton of it and allow the weight of everything anchor it down or do you anchor it in place by other means?

2--Once the skeleton of the wall is complete, how are the "trim" pieces placed for a tight, flush fit? Same glue used in building enclosures or other means?

3--I already have 5% window tint on rear windows on top of the factory "privacy" glass, but want to "black out" the windows so NO light is coming in. Does anyone know what is good to use. I will NOT use paint of any kind as it will just flake off eventually. I have heard of others using black speaker carpet and/or black foam, but I don't want any of the adhesive to be seen from the outside.