Simple glue and nails (or a brad nailer) are often sufficient for decorative pieces. For structural stability, consider using splines or dados to increase the surface area for the wood glue.
When designing your piece, you may need to locate specific functional points: Taniarar
The Missing Piece Puzzle: Why This 'Triangle' Doesn't Add Up polymathematic YouTube• Jan 14, 2025 DIY Wood Triangle Shelf | HGTV Simple glue and nails (or a brad nailer)