This story shows how to avoid getting mounded butt joints with untapered drywall.
Ordinary butt joints are difficult to conceal. That's because the ends of drywall panels, unlike the edges, are not tapered. As a result, you have a seam that's at the finished level of the wall and still requires tape and compound to make it disappear. The risk, of course, is that you'll end up with a mounded joint.
You avoid that by applying a minimal thickness directly over the seam and then working away from the joint with a gradual buildup of compound that makes it hard to see.
But prevention is much easier than cure. You can buy or make inexpensive back blocking products that convert a butt joint into a recessed seam, making it much easier to conceal with tape and compound. If you're a beginner, back blocking is the preferred route because it gives you the best chance of producing a flat wall.
Back blocking isn't just for walls. The technique works well for ceiling panels too. Always use screws to fasten the panels to the back blocker.
Using a back blocker will probably add five or fewer minutes to each butt joint
Power drill/driver or drywall screw gun
Have tools and materials at job site.
Drywall panels, purchased or homebuilt back blocker
When you use a back blocker, stop the drywall approximately in the center of a stud bay and slide the product behind the panel. If the stud bay is 16 inches or wider, you'll be able to position the metal legs perpendicular to the center wood strip. If the stud bay is narrower, rotate the metal legs as far as needed to fit.
Slide the next panel into position, butting it very lightly against the first. Again, drive screws every 6 inches into the center wood strip. Drive a couple of screws through the adjacent panel into the wood strip. In this case, you're not trying to bend the drywall; you're merely anchoring the assembly to the rest of the wall.