Here are the instructions for the square envelopes I made for my Coffee Talk Swaps of yesterday.
These are for 4" cards, but if you pay attention to the dimensions you will be able to alter these to your own size of card.
Cut Designer Series Paper (DSP) (also this is an excellent opportunity to use up the ugly paper you have lying around - i.e. How much of this pink stuff can anyone use - and the DSP pack it came in still has MORE!!!)
Cut at 5 1/8" by 9 1/8".
Score 1/2" from each of the long edges.
Turn paper so that long edge is along top of Simply Scored Tool, and score at: 1 1/2", and at 5 5/8".
Cut out top rectangle as seen in picture, cut to score line at 5 5/8 measurement.
Fold all edges in along score line and round corners of envelope flap and upper edge.
Run adhesive (sticky strip if using the postal system) along lower edge of envelope before folding upwards to form envelope (don't worry if you forget to do this, you will only do it once and then remember to always apply sticky to the shorter seam).
Hope this inspires your own creativity...