starting with flat rectangular panels are doable as Chuck has demonstrated - just another way to skin the proverbial cat
but if you're building a pirogue with considerable flair and need panels similar to the one i've shown, you waste a lot of wood trimming the rectangular panel to the final shape and, with a significant arc cut out of the bottom of the panel, the strips won't be running parallel to the waterline.
OMB, the shape of the side panels is one of several parameters that will eventually determine the final lines of the pirogue. For a given bottom length and width and degree of side flare, less of an arc in the bottom of the side results in more rocker and more of an arc results in less rocker. Changing any other dimension will also affect the final shape, e.g. hold everything constant and making the pirogue wider will increase the rocker - but you can decrease the rocker by increasing the arc or changing the side flare. You have to think in terms of solid or three dimensional geometry, instead of just thinking of intersecting flat planes (two dimensional) that most carpenters work with. If you're building an assymetrical hull, then the high point of the arc moves away from the center of the panel to the widest point.
The profile at the top of the sides is likewise affected by the other parameters. If the top of the side is straight (flat) then the top of the sides of the finished pirogue will have a continuous arc similar to the rockers of a rocking chair. Making the top a more complex shape, other than straight, will vary the "rocking chair"
Anybody can build a hull that will float. The old time boat builders differentiated themselves by building with more complex shapes. Those shapes and the final product was their trade secret and it was handed down to the next generation. Beauty and functionality is in the eye of the beholder and what I like or need doesn't necessarily fit anyone else's requirements