For the only log cabin I've made, I did as Dunster and others have -- cut my pieces to size at the start. Frankly, it never occurred to me -- until now, reading these posts -- that it's sometimes done another way. Mine turned out okay, I think....though it's still not quilted. (Dang those unquilted tops; they just seem to multiply!)
It amuses me, at times, to now realize how little I knew when I began this hobby. It helped, I think, that I didn't know how much I didn't know!