The minimum required for this is a relatively fluffy pillow and enough room to lie out completely flat.
Step 1: fluff up your pillow, and place it as you normally would on your bed. Now tilt it up 90 degrees as if it were going to be pushed up against your headboard. Instead, you're going to lie down on your back and place the small of your neck right in the middle of your pillow. This should cause the top corners to come in toward one another, effectively covering both of your ears and also immobilizing you more than usual.
The rest of the steps are optional:
Step 2: Now you want to create a sense of safety or separation, like being in a tent.
Option 1: Take a second, less fluffy, pillow, and place it on top of the pillow corners that are now acting as support structure directly above your head. You should be able to adjust it so that it blocks most of the light from your eyes without putting too much pressure or having a smothering effect on your face.
Option 2: Take a sheet or blanket and pull it up over your head, draping it on the pillow corners which are essentially serving as tent poles. You'll want to leave some ventilation, but this should basically give you a private bubble to nap in. I actually find that this one works better if you leave your shoes on because the blanket or sheet can then use them as tent poles on your other end.
Of course, there's the conventional wisdom of wearing an eye mask and putting in ear plugs and turning off the lights/closing the blinds and maybe turning on a fan and/or white noise machine. But for whatever reason, having this setup feels more like a pause in the day, distinct from my going to bed routine; in many phases of my life I've managed to be a better napper than a sleeper!