You can use a punch and die set, but they're expensive, or you can very carefully cut around each instrument decal with a scalpel. Very often, the complete instrument panel decal will bed down and conform to raised surface detail with the use of Micro Sol or similar. Depends on the kit though. For example, Hasegawa decals seem to work, whereas Airfix from the 1990s are printed on a very 'stiff' carrier film, and don't work very well.