In one embodiment of the present invention, an assembly for HPHT processing comprises a can with an opening. A powder mixture is disposed within the opening. A substrate is disposed within the opening adjacent the powder mixture. Paint is coated on a surface within the opening and opposite the powder mixture with respect to the substrate. A meltable sealant is disposed within the opening and opposite the substrate with respect to the surface and a cap is covering the opening.In another embodiment of the present invention, an assembly for HPHT processing comprises a can with an opening, a powder mixture is disposed within the opening, a substrate disposed within the opening adjacent and above the powder mixture, a formable sealant barrier is disposed within the opening above the substrate, a meltable sealant is disposed within the opening above the formable sealant barrier, and a cap covers the opening.