Back in 2015 those were some of my first splices. They were lock stitched. I’ve come a long way since then. Here’s a couple tips:
1) I have Samson fids, but I supplement them with size 3, 4, 5, 7, & 10 knitting needles (blunt end cut off.
2) When burying the core, I use a fid one or 2 sizes smaller than the rope. This is key, especially with smaller diameter rope. The smaller fid is much easier to work through the cover area, which can get really tight. I also taper the core about 3” before taping to the fid - this also helps it get through the cover (I tightly wrap the tapered part with Scotch tape). This end of the core is waste anyway.
3) I don’t know how long I’ve been doing this, but I recently realized I’ve been burying the core at mark R and not mark T (see Samson instructions). I’ve always been able to complete the splice to mark R, but there was a sort of slight bump there. Insert core at mark T and that is gone. I don’t think inserting core at mark R compromises the integrity of the splice, but it’s harder to milk it out and looks “off”.
4) I always lock stitch. That takes 2x as long as the eye splice itself!!