Hello,
The best way to get the seat cover over new foam or a seat build up is ......... I hate giving all of the secrets out but the stovebolters need the help! Get some of the painters plastic drop cloths, or rolls of painters plastic and cover the foam on the seat. Turn the cover inside out and center on the seat cushion. Next, slowly roll one of the back corners over the cushion and repeat this step on the opposite corner. Repeat this step for the other two corners as well. The plastic can remain under the cushion, trim off any excess around the bottom of the seat cushion and hog ring into place. Start from the center of the seat and work your way outward. Hope this brief description helps just let me know.
Restoman57