A flexible insulation blanket having a smoothly surfaced, secondarily bonded, ceramic matrix composite (CMC) outer layer, and a method of producing a flexible insulation blanket having a secondarily bonded CMC layer by forming a CMC prepreg layer comprising a woven ceramic fabric layer impregnated with a pre-ceramic slurry and layering the prepreg layer with a flexible insulation blanket. The blanket and prepreg layer are then compressed such that the prepreg layer abuts a rigid smoothly surfaced plate and the ceramic material is cured by heating while under compression. Pressure is then released and the insulation is fired to center the ceramic material of the CMC layer.