Tonight I'll measure the room and figure out the sizes of the lumber I need to purchase. I ordered my wood from Home Depot. My plan is to have the false wall cover the two external walls of the primal room, and then wrap around for a further 4 feet at each end, to cover the first 4 feet of each of the internal walls. That's to make the soundproofing as complete as possible. I've made my decision about lighting.
Some people like their primal room to be completely dark.
Others use a dimmer switch. I don't want to install a dimmer because of my limited home improvement skills, and also because some dimmers make an irritating buzzing sound. So I'll use a simple gooseneck desk lamp on the floor. The lamp itself is black so it won't draw attention to itself. I've fitted it with a 40-watt red colored bulb.