Hi looking for some advice on how to best fit a lintel in our fireplace, i have bought a concrete lintel and have been told two ways to fit it, one being to dry pack it with slate ( which i cant find any) and fill any gaps with mortar and the other way to lay it on mortar and fill all gaps on top with mortar. The wall it will support is only lightweight blocks up to living room ceiling height so not much weight ( new build house with false chimney breast that were making deeper). Any advice greatly appreciated .