I have used at times, bobbin or spools of thread that do not fit on the spindle of my long arm. To remedy this I put a hole in both sides (straight across from each other) of a liquid laundry measuring cup. These come free with any liquid laundry detergent container.

The spindle (tilted up slightly) holds the cup through the holes that then can hold the bobbin or spool of thread which allows either it to turn freely in the cup, although its best to be checking the thread path every so often, iot is also a handy practice to check the needle screw to confirm that it remains tight.