Leave the vac packed meat in the bottom of the fridge for 10 days minimum, 2 weeks max. Give the meat a daily massage at least in the first few days to distribute the cure.
After your desired time give the meat a brief rinse under cold water and pat dry with kitchen roll.
This is where you need some ingenuity. Hang your cured meat in your alpine cave, or cold garage in a UK winter, to dry out slowly and naturally. You want the meat to loose at least 30% of its weight in moisture. It helps if you weigh it at this stage so you can keep track of its weight loss.
An alternative drying method is to use your domestic fridge. In theory this is far too dry and the meat will dry too quickly and harden on the edges, preventing the centre from drying properly. However, if you vac pack it at the point it starts to harden on the outside and leave it for a week or so in the vac bag the moisture will be drawn from the centre to the outside and you can then dry it further. Not for the purists but this does work and it means that you can make Pancetta all year round.
Once dry to your satisfaction slice very thinly and enjoy as a fine starter with some fresh figs, dressed with some good olive oil or however you like it.