Materials will be discussed in more details as the story develops, but for the visble parts of the case there are three main options:
Oak was used for a few of the very earliest spinets in the seventeenth century, notably by John Player, and probably Charles Haward.
From about 1680 until some time around 1760, walnut was universal.
Just a few of the last spinets (e.g. by Baker Harris) were made from mahogany, usually with solid lids and veneered and cross-banded sides.
Whatever your choice, it is worth obtaining suitable timber as early as possible, so that it can continue to season and settle down. Ideally, the timber should be stored in the room where the spinet is to live. This will minimise unpleasant surprises due to changes of temperature and humidity!
These notes do assume that the builder has a certain amount of experience in basic woodwork, and a general set of tools. If you do not have one already, a small bandsaw is the one item that would be most useful, especially for making the keyboard, but for many other jobs as well.
One consideration is that the timbers we use for the case, soundboard, and action are usually only avaiable from timber-yards, and come in the form of rough planks. I can recommend Sykes Timber of Atherstone as a supplier. They stock a wide range of fine timbers, and are sympatheic and helpful towards those of us with special requirements. They do also offer machining sevices, and I would like to offer special thanks to the mill staff for their patience in preparing timber for me. For example, they accurately re-sawed some beautiful 1" European walnut (actually 26 mm) into two ½" boards, thereby achieveing maximum economy.
Often, especially for timber like European walnut, the boards are irregularly-shaped, with just the bark trimmed away. 'Taming' these pieces of wood into a form where we can start shaping and building was once done by hand, mainly by apprentices! But these days we rather expect all this hard work to be done by machinery. It is possible that you may be able to enlist the help of a local woodworking business, but it is perhaps useful to know that in the UK many branches of Jewson's now offer timber machining services. These include surfacing, thicknessing, and resawing (to convert a thick board into two or more thinner ones).