I block things by pinning them out straight on the ironing board (the fabric holds the pins well enough and its kid and pet safe), then spraying liberally with cold water from one of those plant misters. Just leave it until its thoroughly dry. Sometimes I put a dry tea-towel on top to stop it drying out too quick.
If the ironing board isn't big enough, just do the top half, then the bottom. Just spray where it is pinned.
It does straighten things out nicely, and the yarn seems to have a 'memory', it'll return to that nice straight shape next time you wash it and lay it flat.