While there are several different ways to add a new thread, I am joining by overlapping. Since this cloth that I am weaving is considered to be as "utility goods", I didn't see any need to get real fancy. According to my notes, "this cloth while woven with cotton and linen was referred to as fustian", it had many different threadings and treadlings. Fustian was a catchall name.
Not very noticeable with this choice of sizes of threads.