oven opening and floor?

[mark4604]

Hey everyone, it seems I need to re size the opening of my oven because it?s to large causing heat loss and smoke exhaust problems. Also I need to put a new floor inside because in my blinded stupidity I forgot about the under floor insulation. I am wondering what material I can use to close off the large opening of my oven sense it?s just a little space? I can?t really afford to buy more refractory concrete here because it?s amazing expensive, so I?m wondering does anyone have any ideas. Also what material can I use for the floor because I can?t find fire clay and well I already explained about the refractory concrete problem. So can anyone offer any easy fixes? Or at least some less costly ones? Thanks everyone putting up with an amateur!!!