This is more of an experimental method – as the blogger posts, you need a sense of humour because chances are you’re going to wreck something – but it works like a charm. The secret ingredient is the fizzy tablets, like the ones for dentures but I imagine pop rock candies work, as a bead core. The bead is formed and baked over the tablet, leaving space for it to fizz out. Once the tablet is all fizzed out, you can cover the gap with a new bit of Fimo clay and bake again.
I may do it just to see my beads explode… In the same sort of way you can use cornstarch pellets or paste, form and bake a bead. Leave a hole or drill one after and toss the mess in water. The cornstarch washes away.
The regular note: the link goes to a translated page but the original German one is here. The pictures are fairly straightforward.