I have just had a chimney liner fitted and was advised that I can fix the liner to the mouth of the fireplace by inserting a rod either side and sloping a slate inwards on each side to rest on the bars leading up to enterance of the liner. Then backfill and seek around and to liner with a lime, cement, sand mix is this a known method using the slates, he said it was to guide the smokeup to the liner. Is this good way to do it? Won't the slates crack, is it fire safe?
you can buy a proper metal fume collector hood which you fix to the end of the flexible liner and then fix to the roof of the builders opening and cement in to completely seal.
or you can use a metal flue box, depends on what sort of fire your going to be fitting.