The first and most important step in constructing a peanut butter and jelly sandwich is the selection of the bread. This is the skeleton of the sandwich (exoskeleton, perhaps?), the thing that holds it all together. The bread must be firm enough to provide some support, yet soft enough to give a good texture to each bite.
With a knife or spreader, apply peanut butter to one side of one slice of the chosen bread. The knife should be wide enough to effectively scoop the peanut butter from the jar, and it need not be sharp. Enough of the peanut butter must be used to apply a layer roughly 1/16″ thick over the entirety of the bread slice. Overlapping the edge of the bread is allowed, but be prepared to clean peanut butter from any nearby surfaces.
When you’re finished with the peanut butter, clean off the knife to avoid cross-contamination (wiping the peanut butter off on the other slice of bread is acceptable). Then spread a thin layer of jelly on the second slice of bread. The jelly need not be as thick as the peanut butter, unless you’ve got a serious sweet tooth.
Now the final assembly of the sandwich can be completed. As the peanut butter tends to be stickier, I prefer to lift that slice up and lay it atop the jelly slice, face down of course, in a way that minimizes overhang. The sandwich may now be consumed at your leisure, accompanied by your favorite chips and the beverage of your choice.