From the pictures, the top ends of the knots look very even. A second picture with a rotation would be helpful.
But, from what I see, all is good.
Only process suggestion I have, and it does not seem to be a problem for you; with whatever sled you are using, make a bunch of practice cuts to get the feel of where you need to put pressure on the sled to keep the cut even. For me, I use a 35 yr old Craftsman table saw. It is in good shape, motor is solid, and I just need to get the right amount of pressure on the sled for even cuts. When I am "on," I can get even slices down to .050"
Even slices are not needed for Celtic Knots, but each cut you make needs to be repeatable. Just a matter of practice.
But... your pens look great!