We have used firebrick splits (half thick@ 1.25") for some time in our commercial oven. I just set them side by side on the rack, 2 rows of 4. Since the oven is quite large there is open space on each side as well as a little in the back & front. They need to be preheated for at least 45min to 1 hr. I'm not sure what the upper temp limit of an unmodified electric oven is.
I didn't find our oven hot enough & moved outside to a Weber with charcoal, then switched to gas. Search "little black egg" for Villa Roma's excellent posts with the same thing or
this one (Anyone ever made Weber Grill Pizza on a Stone?) I posted.
I have had the best success with this set-up.
Ted