This is not so much a step by step or tutorial, I just thought I would let you know how I get the 3D looks onto my layouts.
Of cause my favourite go to is chipboard, but I have a couple of other tricks I like to use too.
Step one is to play around with positioning your elements when you are happy take a photo with your phone or camera so you can refer back to it when putting the pieces back on. I usually make changes as I go still but it gives me a good reference.
I have a couple of favourite products I use for added height. Scrap Dots is one I use a lot behind chipboard if it is not solid enough for foam tape.
Or if I want more height than I can get from foam tape.
Another item I use is good old cardboard box lids. I do not use it directly behind a photo always with a paper buffer. It allows me to have full coverage under the entire photo mat so there is no dips or blips in the layout later on when you look back at it.
Hope these come in handy for you.
Thanks for looking