With today's glues, a simple butt edge joint works just fine. The boards need to be jointed well (the edges very straight, and I like a slight hollow towards the center ensuring the ends are tight and don't gap in the future). Clamping cauls will keep the boards aligned (I make my own from fir 2x4's). There will always be a slight misalignment of the boards at the joints that will need flattening (the same using splines, dowels, biscuits, or nothing). Sanding (by hand or random orbital sander) can work, but takes a long time. Some cabinet shops can sand or plane wide panels. I use hand planes for this step.
Many believe splines, dowels, or biscuits strengthen the joint, and they do not. A butt edge joint is just as strong. These methods can also cause the underlying dowel, etc. to "telegraph" into the finished top due to dissimilar wood/grain direction, etc. As for alignment, I have used each of the methods, including routered glue lock joints, and simply edge joining the boards and using clamping cauls to align them provides the easiest and most aligned assembly of all the methods.