Make sure to immediately clean up any excessive glue from the marble countertop.
Install marble countertop on the wall.
Kyle you should install some sideways 2x4 or metal cross bracing under the plywood that extends from wall to wall at or near the front and again half way back of the countertop.
Step 1 take proper measurements.
Measure the area in which you want to install the counter top.
This will remove all dust.
If the countertop is too large or too small contact the manufacture to adjust the fit.
They are fairly easy to install and you will be very happy with the result.
Measure from the wall to the edge of the cabinets in multiple spots for both the width and length of the countertops.
Apply a wet wipe using alcohol run across all marble surface area before using the adhesive.
If the fit is too large you can try to cut it to the correct size yourself with a circular saw but you risk splitting the marble.
Step 7 dry time allow the countertop to set overnight after examining the installation to make sure an even consistent bond has been created.
Pay attention to any wavy walls or out of square walls because they will effect the installation.
Lay the marble countertop over the wood vanity to trial fit for shape.
Record both the length and width.
You need a completely solid and stable base for the marble slab.