I made this jig to hold the necklace found on the xtool website. With this jig the neckless sits flush on the wood. I made it out of 1/4 inch birch plywood from home Depot about 6mm. I ran everything one time then I turned off the input for everything but the engraved parts and turned down the power to clean up the engraved part and to get a little more depth.
After you run the file the first time you need to turn off the output on everything but the engraving and run the engraving again at a lower power to get more depth and remove some of the darker burnt wood. the first pass I used 75% power 250mm speed and the second pass I used 50% power and 300mm for the speed. The power and speed might have to be adjusted depending on the wood you use. The ambient humidity will effect the dept of the engraving you might have to run the engraving part multiple times. Make sure the last engraving is ran at a lower power and higher speed to give a cleaner part.