Don't forget the wood specie has a lot into how much the wood warps. Redwood and cedar don't warp much. Spruce ( the most popular wood used for paddle) warp and twist a lot. All recommendation above are true. In terms of importantance: straight grain, specie, dryness when work on.
Ps: I suspect the finish may affect how much it warp, too.

: hello everyone!
: while i wait for my epoxy to cure i decided to buy a "top choice"
: 2x6 and make a greenland paddle. it is/was going good but i noticed that
: when i cut out the loom part the hunk of pine is warping. i think i cut
: away some of the grain that kept the hunk of pine straight. now i know why
: people use laminations, switch the grain up to avoid warp. is this warp
: part of "the deal" with traditional paddles? should i just leave
: it? ideas anyone? i thought of finishing the paddle, soaking it in water,
: then clamping it down to my work bench. if i do this, will i have to do
: this every time when i use it?
: cluess, bent, and left handed,
: brett the hitman hart