Japanese tea rooms can be various sizes, which are expressed in terms of the number of tatami mats that comprise them. To keep my mobile tea setup physically manageable, I decided I'd go with a simple, small, two-tatami mat space—one mat for the host, and one mat for the guest(s). Having made tea for friends before with a two-mat setup, though, I've found that personal space becomes a challenge. I've never had tea class in such a small space, so I've never seen an authoritative solution, but the problem in a small space is the lack of what I'll call neutral territory. The distinction between space that is inside the tatami border (relative to the guest or host) and the space that is outside that border is important. The space inside the border is basically your personal space. When there is no 'neutral territory' that is outside both the host's and the guest's personal space, the act of placing something like a tea bowl outside your space—as the host would do to serve tea to a guest or a guest would do to examine the bowl—becomes the act of placing something inside someone else's personal space. Which as far as I've seen is not done, except marginally between guests. It feels invasive.
An attractive architectural solution is for the tea space to include a naka-ita (literally "middle board") between the host's mat and the guests' mat. This board provides neutral territory, so a host can serve a bowl of tea without putting it inside the guest's personal space, a guest can examine or return utensils outside the tatami border without putting those utensils on the host's mat, and the guests can pass a tray of sweets amongst themselves without impinging on each other's or the host's personal space.
This is a long-winded explanation of why I'm undertaking the project of making a naka-ita, which will be useful not only for this tenriki-no-cha project but generally anytime I want to serve tea with a two-mat setup. I found some beautiful cherry boards at the Woodworkers Club store; since none of them was wide enough, I joined three of them with glue and clamps. I'm currently in the sand-and-apply-finish loop, so I'm getting to know the nuances of this piece of wood intimately. Even on a surface that looks and feels smooth and level, sanding after applying finish reveals subtle variations in the surface, whether brought about through the natural growth of the tree or through the planing process at the wood shop. I'm guessing that I'll be 'done' once enough finish has accumulated and/or raised the wood grain such that sanding no longer reveals new surface variation. If you're a woodworker, your input is more than welcome.
I'll rub on a finishing wax afterward and, since the inch-thick board is not quite half the thickness of a tatami mat, create a (styrofoam?) underlayer to bring the board level with the surface of the tatami mats.