Solid wood is a varied category since the types of wood you can purchase ranges so much. Generally solid wood is more expensive than the other wood products like plywood or MDF, the pieces available are also more limited to board sizes so you won’t be able to get a large flat sheet like with plywood or MDF unless you glue up a bunch of boards and plane them flat which is a lot of work. Solid wood can be more inconsistent than other wood products, avoid knots and shifts in wood density as this can affect the laser’s ability to cut consistently. Low-density woods like basswood cut extremely fast while high-density woods like purple heart just laugh at the laser tickling the surface 🙂 For engraving it is usually a good idea to pick a lighter wood in order to get a good contrast with the engraved area. It’s also a good idea to pick a board with a consistent and even grain pattern as the rings of the tree will be harder and engrave away less than the sap wood which is softer and will engrave deeper. This can be used for effect if that is what you are going for but fr an even engraving look for the right cut direction and grain pattern. And definitely make sure the board lays flat so the laser can maintain a constant focal distance, otherwise you might need to plane it in order to get a good result.