shower pan construction...HELP!

when building a shower pan for a standing shower 36x36 is it ok to just do a mortar bed and then waterproof with redgard before tiling or do i need to do the standard mortar , liner, mortar pan. There seems to be a lot of debate about doing it the old known way but a lot of people are saying a shower pan now only needs to be mortar and then covered in redgard before tiling can start

any help here from anyone would be appreciated