I am short and most of my height impairment is in my legs. So getting good ergonomics with my work tables has always been difficult. I have dreamed of a custom sewing table (I need 3 actually) for a long time but neither Chris or I are very handy in the carpentry department.

This is how I have been working and it's worked fairly well. I use plain folding tables and Chris built me these boxes for my presser foot. I set my chair as high as it will go and that gets me pretty close. Except that my chairs really won't raise quite high enough for me and then they are totally uncomfortable for other use.
I have 3 folding tables for 2 machines and a serger and they are all set up this way. I recently found adjustable table legs from Ikea. I ordered 4 and tried them on my Pfaff sewing table in April and I loved them.
Around the same time we decided to get rid of our big entertainment center because it would not hold a big TV that Chris wanted. (OK, I will want it too come football season.) You know that entertainment centers aren't worth much so instead of selling it I decided (while Chris was out of town) to completely dismantle it and see of I couldn't use some of the parts for other things. Chris wasn't much interested in that project idea but I found use for some of the items and the rest (all particle board) went to the dump. I used the drawers for bins in my dye studio and I saved the top because I thought it would be a perfect sewing table with a cut out for my Juki machine.

That's the underside of the top and it stayed in the middle of the loving room floor for about a month until I could talk him into the sewing table project. Thanks to the links you shared we finally formulated a plan that we could reasonably execute.
Before I share what we did I will tell you that this is the redneck method of construction. When it comes to my sewing room space I am totally function over form. I'd love to have the beautiful space that Karen has, but I don't have the patience to take up any of my time painting anything; just not interested. So until someone comes to my house and magically creates a dream sewing space for me I will stick to my simple but highly functional room!
Here we go. The only purchased materials that went into this project are a few 1 x 4 boards, some hardware and the Ikea legs.

First we borrowed a jig saw. I measured my Juki carefully and created a template for the opening. I determined that I wanted the needed to be about 8" from the front edge of the table and then traced the outline. I taped around the outline because we were concerned that the veneer might chip...but it didn't. We rested the table on some bricks so that the saw blade didn't cut into the work table.

We (he) glued and screwed a 1x4 on the front and back edges of the table top. The table is veneered particle board so it's not strong enough on it's own. Let's be honest here, I was mostly watching at this point.

For the machine shelf we used some 1 x 10 fir boards that we had around the house. When we moved into this house the living room was completely full of book shelves. We took them all out and are still using the wood 12 years later!
He cut the cross pieces first and we positioned them in place. Then we positioned the shelf on top and drilled the 6 bolt holes through both layers at the same time. We inserted the bolts and then put the whole assembly in place: glued and screwed.
He made that shelf extra wide so that I wouldn't be slamming my knee into those bolts every time I sew.

The last step was to put the leg bases in place. I used one in each corner and one in the center of the back. I may decided later to add one in the center of the front but it all seems fine now. The hardest part was adjusting the legs. These legs work great and are very economical but the trade off is that they are kind of a pain to use. But I figured it out and we eventually got them set right. The nice thing is that I can work with this for a while and determine if I need any more adjustments.

I didn't even paint the front edge of that 1 x 4. It works great! We did use one L-bracket on the back to make it more stable. These kinds of table legs are inherently wobbly so a little bracket is very helpful.
This table is smaller than the old one (as I wanted) so it's giving me a little more floor space to work with.

I also got my serger table done and now I have a little more storage space under there too.

I saved a few more parts from the entertainment center. It had these nice black shelves so I used some bits of scrap wood and made a little frame on the back side of the shelf.

The shelf fits snugly on the top of this rolling thread cabinet. Now when I am binding a big quilt or just need a surface for laying out blocks I can roll this extension table in place next to me. I've already used this a few times and it works great.

With the smaller sewing table I was able to rearrange this corner a little bit and now I have room for my computer in the sewing room. It all worked out nicely and we didn't argue even once! See, miracles do happen.