Alright, I now know I should have used plywood for the countertop. Live and learn.
I now know that I should take countertops outside and apply laminate to the countertop.
Question is should I put countertop seam as close together as possible and saw a new seam to get a tighter fit. This is how it looks now.
Here's what I would do. If you can have a helper handy when you are done laminating to help carry and place the top, that would be great. If not, you could do this in place if necessary.
First, I would glue and install to the underside of the front and back edge ¾" plywood, 2½" wide to get a front edge buildup, and space up the back edge. This is also used to screw down the top from the underside when ready to install. Hold the back edge in abut ½", in case you have to scribe it to the wall. If you have held the back support ½" in, put a small section of ¾" plywood at the very end, so when you laminate the edge it will be solid all the way to the wall. If you don't there will be a notch in the laminate.
Install the underside buildup piece right across your seam in the substrate. Cut a scab board out of ¾ " plywood to cover the PB seam from the underside for about 6" in both directions. Glue and screw it on both sides. Make sure your screws are the correct length.
I would then laminate the front edges first, and sand off flat to the top. When laminating the top, I would run the seam from the left 90° corner on a 45° into the back corner. Joint both mating edges with a straightedge, and check for a fit. An alternative to straight edging the mating edges would be to cut a miter on both sheets about ½" long. Clamp the sheets about ⅜" apart, mark across both sheets some alignment marks with a pencil. Run a trim router bit on a straightedge between both sheets at once. When done, backfile them to dress them clean.
Apply a solvent base contact cement to both the PB and the laminate. When the glue has flashed dry for about 20 minutes, check both surfaces for any debris, and check the mating edges of the miter for glue globs. Those edges should be clean. You could back file those edges so the top surface will touch without a problem.
Lay on the PB some ½" dowels about 10" apart to keep the mica from touching the PB. That will allow you to get some overhang all the way around, and align the pieces for the seam. Have a line drawn on the PB for the seam. Lay the edge of the 45° on the line, and slowly and lightly start taking out the dowels. When you are ready to put down the left piece, lay a ¼" dowel parallel to the seam line about 10"-12" away, and touch the edge to the seam. Then pull out the dowels slowly leaving the ¼" one. That will leave a hump type bubble when you slide it out, which you will gently start pushing down forcing the edges to become tight. If you haven't pressed the entire sheet down, you can get some movement from it. If it's too tight, it should be lax enough to move back to flatten out.
Once the top has been laid down, use a "J" roller, or the edge of a block of wood and press down hard from the centerline out to get all the air out. Then use a handheld router with a flush trim bit with a bearing to rout off the overhang. Use a mill file to dress the mating edge, filing only on the down stroke. And, there you have it.
NOTE: Laminate used for countertops would be best if you use 1/16" laminate. Laminate for doors, and cabinet faces is 1/32". They are in many cases available in the same color and texture. Sizes for 1/16" can go up to 5'x12'.
You can apply the contact cement with a brush, or a 9" short nap paint roller (adhesive type roller cover). Work in a well ventilated area.