Cut a rectangle out of pad 45" long x 9" wide
Score rectangle at 16 in from each end so middle panel is 13" wide. Don't cut all the way through., just enough so foam will bend and make 90 degree angles
Drill or poke 1/8" holes : holes 4" & 8" up from bottom and 4" & 6" up from bottom and 4" up from bottom on each end panel.