QGIS Bare Earth Tutorial

I have QGIS desktop 3.26.3 and would like to perform a bare earth assessment of site ~11 hectares in size. The site was flown using a Mavic 2 pro and images processed into an Orthomosaic. The bare earth is to be represented as a fraction of the total area. A snapshot of the ortho (a 1.2GB ortho is available) and KML file is attached. I would like a simple tutorial that is simple to follow and easily replicable in QGIS.