The best way to level a sink as you install it would be to add a sink base. Or a sink cabinet. What you will need to do is allow enough room for the cabinet. Once you have enough room for the sink base, your cabinet will have to be around two inches on all sides of your sink for the base, if you want a bigger cabinet then you need to figure that out and make all the sides even otherwise it will be off balanced. There are a few supplies that you will need to do this project. You'll need a stud finder, a carpenter’s bubble level, a screwdriver, and a lot of patience.
Once you have all that decided you’d want to find and mark your studs that are in the wall. How do you find the studs? Well, there are two options here you could use a stud finder or you could even tap on the wall until you find the studs. Mark the stud with a pencil so you can remember where they are. This next step isn't hard at all, you will want to adjust your sink into the position you want it. Once it’s in position you will want it held there so you can move onto the next step. Make sure that while it is being held in place that it does not get moved otherwise it will be off level once more.
Now here is how you will level your sink. To level your sink you can use a leveler or even use a straight piece of wood and let it rest on the sink with a bit of an overhang to test and see how straight it is. If it is not level use smaller pieces of wood, or buy some shims to make your sink turn level. Do this all around the sink as it could be level in the front but not in the back or even on the sides. This will also serve to level the base of your cabinet as well.
Once you have your sink leveled off, you will want to screw the back of the sink base to the wall with the strip that is given with the sink. This piece will be wood that will go down below the back rim of the sink base, if you made marks on the wall then use those as guides for where you can put your screws into safely... That is the most secure way to install the base of your sink.
Now that you have your sink level, you can add your cabinet doors, and finish off the plumbing and as well as putting your sink top on and perhaps even a countertop to make it look even more professionally done. Make sure that your sink is level; keep looking at the carpenters bubble to make sure. You can now use your sink after you hook up all the plumbing.