There are basically two reliable ways to make lids for decorative boxes - veneered plywood or solid timber frame and panel construction. I use both methods according to needs, and you will see examples of both methods on my website.
Veneered plywood. In this method, thin plywood is veneered on both sides with natural timber veneers, cut precisely to size and set into a solid timber frame. The downside of this method is that it is more time consuming and more exacting then constructing a solid timber lid. However it has 4 distinct advantages.
1. Plywood is an extremely stable material, so the lid is not vulnerable to warping, splitting, cracking or simply falling apart due to the effect of natural expansion/contraction.
2. It allows the use of rare and striking timbers, which would be prohibitively expensive or simply unobtainable as solid timber. Examples are the various burls and ebonies which you will see on this website.
3. This method can give a smooth, uncomplicated, modern look to a box. Usually the veneered surface is set level with the top of the solid timber frame which surrounds it, to give a flush-across-the-top look.
4. This method is environmentally sensitive. Most highly decorative veneers come from rare or threatened rainforest tree species. One felled log can produce thousands of metres of veneer - a sensible way to use a precious resource.
Solid timber frame and panel construction. Solid timber is inherently unstable. Long term drying-out, as well as seasonal fluctuations in temperature and humidity, cause it to crack, split and warp. Further, the seasonal fluctuations mean the timber is constantly expanding and contracting - not visible to the naked eye but producing very strong forces nonetheless, and easily able to split apart a lid that has not been designed correctly. Except for the very smallest boxes, to use a simple slab of wood as a lid is not really viable, it will almost certainly warp or split over time giving an unsightly effect. Instead a method must be found which allows the solid timber to expand and contract unrestrained, but still appear as an attractive structural unit. The most suitable method is frame and panel construction, whereby the flat solid timber of the lid (the panel) is captured (but not fixed) within a solid timber frame. The panel has thin tapered edges, which are set into grooves in the surrounding frame. The panel is not fixed in place (although it may appear to be to the casual viewer) and has enough freedom to expand and contract with changes in weather. If the ability to expand were not designed-in, the panel would eventually split the solid timber frame apart.
The major disadvantage of this method is that the lid has a groove around the outside where the frame and panel meet. Also, its use is limited to rather plain and unfeatured timbers, as burls etc are not really suitable for making into thin panels. Its major advantage is that it is quicker to make and does not require the skill level of veneer work. Further, it appeals to people who must have solid timber, for whatever the reason