Lots of options, but two main ones, and an outfield thought:
Transfer paper/masking tape is a great option. Stickiness on the tape is about pressure, usually, so if you have a felt squeegee - or even an old gift card, though it can be a more delicate process with those - be sure to start from the middle of the taped area and with firm pressure slide your card/squeegee to an edge. Then move back to the center and repeat those straight, firm strokes in a circle, making sure all the adhesive’s getting a chance to stick on. Then burnify that wood : )
Second option:
Multiple passes at different power/speed/hz. You can dial in the settings to give little scorching, especially by do a set of three passes, each one only burrowing through the wood about a third of the way. (Another option here, once you get comfortable with doing it, is two passes, a light one to break the surface and a second of the precise settings combo to just barely destroy the rest of the wood in the way of your design. This keep the surfaces from taking the brunt of the obalted material, as on the second pass much of the soot is trapped in the kerf)
Left field:
Paint it before hand, and anything other than a light, flat color will often hide small scorching.
Oh, you can also clean it off the piece afterwards will a little bit of water, usually; Murphy’s Oil soap, if you have a lot of heavy burn. : )