Hi Riverrailfan,
I used blocks of foam cut to fit. I find the foam in the 'florist' department at Michael's to be the easiest to use. For the LED lights, I bought battery powered strings of LED lights from the 'Dollar Store', they take 2 AA batteries. (for giggles I left one string on for the past 2 weeks and it's still going bright).
I then pushed each bulb through the bottom of the foam until it just about broke through to the surface. I then covered the foam block with white 'snow' sheet, also found at Michael's. A little hot glue to hold the white felt in place and done. One additional step was cutting out enough foam underneath the block to fit the LED light battery pack.
I cut the foam to fit snug, so all I have to do to turn the lights on is lift the block out to reach the battery pack on/off switch.
