I make tissue boxes mainly these days because I do not have space or room for any additional items in our own home and boxes seem acceptable to give and usually these gifts are reciprocated in many ways.
The moisture meter I am using is a loan by a member here, one of those reciprocated gifts, model CNY290 and is keeping me in touch with moisture conditions. This mainly came about because a neighbour gave me 4 handy sized logs from ash trees growing on their property (another amicable arrangement) and Marcos kindly thought that I would put the meter to good use over the winter.
Yes I do think you need to watch timber moisture, it needs to be stable and somewhere in the 11% moisture range for small boxes, these boxes do not have parts that open and close so condition is not perhaps as critical as drawers, lids and doors.
If timber is still high when I begin again in the Spring, as mentioned I will only prepare small strips and use drier timber for the wider parts.
Greyorm I am sorry I missed your post on the 15th but I usually retire in the afternoons these days so unfortunately yours was not seen.