I have learned a lot from trim carpenters about methods of work and materials. One example is Azek cellular PVC for outdoor projects. Using wood outside, whether painted or stained, is always problematic. I’ve seen cypress and redwood rot where water collects.
Azek is a smooth surfaced cellular PVC that cuts and routs just like wood using carbide tools. The special Azek glue works for cope and stick joints, butt joints and laminating pieces together to get thicker materials. It comes in 4’x8’ sheets and dimensional material of 1/2”, 3/4”, 1” and 1-1/4” that is 18’ long. It is available at most lumber yards, but not at Lowe’s or Home Depot.
I use 18 gauge stainless steel brads and stainless steel square drive screws as fasteners. Pocket screws work quite well. It isn’t meant for structural use so that is a limitation. It is not inexpensive but in my book well worth the money. Miter joints stay tight and don’t open up. It never rots. It takes paint very well but doesn’t have to be painted if you like the white color as is.
Below are photos of a garden obelisk and a window box I made last year. The window box was made using standard cope and stick router bits and a raised panel bit, just like making cabinet doors and glued using the Azek glue. I love Azek for outdoor projects. It is a joy to make a project once and know it will never need painted and will never rot.