I would wash and dry the panel to see what it wants to do "on its own" Sometimes it will go "on-grain" by itself.
If it went "on-grain" - then I would just square it up as well as I could following the grain lines.
It looks to me that there is a bit of wiggle room on the background.
I have found - for myself - that keeping grain lines perpendicular to the edges - makes for an easier to handle project.