If you're interested, the way I made this is:
- Take two pieces of high quality 1/2" pine plywood
- Cut a hole in the top piece using a 3/4//" drill bit for pilot holes and a jigsaw (My sewing machine came with a quilting extension table, so I was able to cut the hole to that size, giving me more wiggle room for the machine itself).
- Use 2x4s to build a structure around the hole, overlapping by 1/2" (so that I can put the piece I cut out back over the hole if I ever need a flat surface, the 3/4" holes leave enough space to easily get the cover on and off). *Make sure that you leave an opening in the structure where your sewing machine's cords can easily come out.
- Secure the structure to the table top using pockethole joinery so that the table surface remains smooth
- align bottom of table to the top and secure to the framework with regular screws ( I used a countersink drill bit so that the screws wouldn't stick out
I might write up a full blog post tutorial at some point.