Hey!
When u hover over an element, there is a "class" button. U can use that for custom css styling. Here's an example "create a custom button style": http://laytheme.com/documentation.html#custom-css-styling
In Lay Theme, normally an element will always overlap a preceding element.
Also elements inside a row will always overlap elements of a previous row.
With the latest lay theme version you can also right click an empty spot of a row and set a row class. That might help with some z-index things you want to do.
