Can’t quite work this one out, need more accurate information.
If you’re referring to overshoes being worn with SPD SL ie road shoes, then you shouldn’t be walking in them at all as the shoes really are not for walking in.
If you mean overshoes being worn with SPD shoes ie MTB or possibly touring shoes then the elastic edge of the overshoes normally fits around the bottom edge of the shoe soles and a middle velcro strap passes under the shoe, between heel and sole, high of the tread, so that with a little adjustment no part of the overshoe needs to touch the ground when walking.
I have a couple of pairs of Northwave overshoes which work like this which I have had for years, but general advice when wearing cycling kit would be ride don’t walk ;-)