Cut bell of Ireland stems when the bell-shaped leaves are fully formed and look just like you want. Cut them in the morning near the bottom of the stalks, but wait until after the dew has evaporated.
Tie the bottoms of the stems together with twine to make a bunch. Pipe cleaners also work well. About six to eight stems tie nicely together, so divide bells of Ireland up as necessary to tie together manageable bunches.
Rig up a string line in a dry, dark, cool and well-ventilated space to serve as the drying environment. Your garage may work. To rig up a string line, tie it to a nail, for example, on one side of the room. Then string it to the other side and tie it to another nail.
Clip the bottom of the bunch upside down to the string using binder clips or clothespins. Leave the bells of Ireland there until they completely dry, which takes one to two weeks depending on the humidity levels in the room.