Here is a circle flap envelope svg by request from the SCAL forum. This envelope is in 6 parts so that it can be used for large square cards or cut with the baby bug. Score, fold, and attach the half circles to the larger square, then cover the attachments with the smaller square.
The download is a zipped folder with svg files for use in either version of SCAL. These files are for personal use only. Feel free to link to this post, but the files are not to be shared or distributed in any way.
Download the files from here.