For the crust, are the graham cracker crumbs, butter & sugar measured by volume or weight?

Solid ingredients are measured by weight, as opposed to liquid ingredients which are measured by volume. It gets confusing because US customary measurements use the term ounce in both cases. The butter is best measured by weight and then melted, which is easier- and the slight variance is not that critical. You will need a scale for all of it, rather than a measuring cup marked in ounces.