Apply Joint Compound to Seal Seams and Imperfections

What happens here

Apply a generous layer of joint compound (also known as drywall mud or spackle) to all seams between OSB panels. Use a putty knife or broad knife to spread the compound smoothly over the joints, feathering the edges so they blend seamlessly with the rest of the wall. Also, use joint compound to fill any remaining nail or staple holes, small divots, or rough patches in the OSB surface. Allow this first coat of joint compound to dry completely according to the manufacturer's instructions, which can take several hours depending on thickness and humidity. This step will likely require multiple applications and drying cycles to achieve a perfectly smooth, drywall-like surface.

Goal: Fill all gaps, seams, and imperfections on the OSB surface to create a smooth base.