i always cut my setting triangles so i do not have bias edges along the outside - if i do have to (handle) bias edges at all i do starch- but no steam-which tends to distort them without any handling. but i do work hard to avoid having to handle any bias edges-

What I do:

Starch or Best Press the material before cutting.

Yes, do a basting stay stitch to stabilize the edges. Without this it is too easy to stretch the bias.

ali