with the concave forming surface 105 of the mold part facing downwards the back surface substrate 201 can be disposed symmetrically on the bottom of the front surface substrate 101 with the convex forming surface 205 of the back surface substrate 101 projecting partially into the concave region of the front surface substrate 101 preferably the back surface substrate 201 can be dimensioned such that the convex surface 205 thereof engages the outer edge of the concave surface 105 of the front curve substrate 101 throughout its circumference thereby cooperating to form a sealed cavity containing the saline solution 301 and the oil 305 referring now to fig4 ultra thin optical pieces 102 and 202 assembled and sealed together containing one or more liquids therebetween according to aspects of the present disclosure are depicted the front curve substrate 101 and the back curve substrate 201 are assembled together forming the mold assembly 400 used to join the ultra thin optical pieces 102 and 202 with the saline solution 301 and the oil solution 305 therein in some embodiments the mold assembly 400 may include a groove 401 in one of the substrates 201 or 202 that can be used to deliver an adhesive used to seal the saline solution 301 and the oil solution 305 between the ultra thin optical pieces 102 and 202 in alternative embodiments the.