The common method of cutting celtic cross glue ups is to use a circle saw with a thin kerf blade, however the contrasting wood must be the exact same thickness as the saw kerf to maintain alignment of the 4 cuts required. The smaller say from 1" (25mm) or lower that 1/8" (3.175mm) thick is way out of proportion.
The idea I tried is to use a slitting saw and the one I had from Harbor Freight is 2" (50mm) diameter X 0.04" (1mm) thick X .25" (6.35mm) bore, which I already had mounted on a .5" mandril.
The first try I decided on was 1/2" (12.7mm) squaire and to add more interest I used maple and walnut and that also allowed cutting the inserts from the same stick.



The first picture is making the third cut. The blank is inserted into fixture tight against the walnut plug in the bottom then clamped in the milling vise and brought towards the operator to make the cut. The cut complete move to photo 2, apply glue to the two ends, put the insert in place, snug up the clamp. The third photo fold the plastic over the joint, add the little bar clamp and the top clamp block and tighten all 3 of the clamps. the glue is set enough after about 3 hours than repeat until all 4 cuts have been made.
The idea I tried is to use a slitting saw and the one I had from Harbor Freight is 2" (50mm) diameter X 0.04" (1mm) thick X .25" (6.35mm) bore, which I already had mounted on a .5" mandril.
The first try I decided on was 1/2" (12.7mm) squaire and to add more interest I used maple and walnut and that also allowed cutting the inserts from the same stick.



The first picture is making the third cut. The blank is inserted into fixture tight against the walnut plug in the bottom then clamped in the milling vise and brought towards the operator to make the cut. The cut complete move to photo 2, apply glue to the two ends, put the insert in place, snug up the clamp. The third photo fold the plastic over the joint, add the little bar clamp and the top clamp block and tighten all 3 of the clamps. the glue is set enough after about 3 hours than repeat until all 4 cuts have been made.