How much customization do you want to do and how much work do you want to do? Since the truck probably had a rubber mat with slits in it when it was new, it doesn't matter whether your carpet has slits or not. There is no right or wrong way to install something that didn't come with the truck when new.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)