Hi DaveP. Just a couple things I find helpful. Place a square along the outside of the corner joint & clamp the angle iron or tack it to the workbench out past the ends of the square. Then tack & weld the joint. If there is any gap to fill , a small tack or a piece of bare welding rod tacked into the gap before welding will help stop the contraction of the weld metal ( leads to the distortion of the 90 degree corner ). You could also allow for some distortion which seems to always happen anyway by setting the joint up a little wider than 90 degrees initially. Also, welding from the centre of the joint to the outside edge will also cause less distortion than welding in from the outside end of the joint. If you weld with enough heat on both sides you shouldn't have to bother veeing or bevelling, but if you want to you could grind out the joint with a grinder before welding to improve penetration. Have fun - WS