get some insulated wire  almost any gauge works.   mixed gauges spliced together works too.
More wire is better

What size ring?  It doesn't matter.  make it as big as you want.

wrap it in a ring.  It's OK to solder splice wire segments together - just tape the joints.

Wrap many circuits  of wire into the ring - I don't know of a theoretical maximum but no less than twenty coils is good.

Fetch an unused power cord like what you cut off a busted appliance

Put a switch on the hot side.  Put a small light socket  in the circuit.  Use a low wattage - lower is better. I just needs to operat on line voltage.

Tape the ring you made together, attach the ends to the hot and neutral leads from the power cord with the switch and light bulb.

You have made a controlled and safe degaussing coil.  You can mount in wood and make it into a regular appliance.

The AC pulses through the wire creating a magnet field that oscillates at 60 htz.  Passing a magnetized metal tool across the flat ring degausses the tool.

The light bulb is not an absolute requirement but it makes it safe.  Without the bulb the ring would get hot rather quickly forcing you to work fast and unplug it quickly.  Lower wattage bulbs create a stronger degaussing field.

I remember those early days of color TVs and the big old CRTs- before they built in the degaussing  circuits. Every house call required the use of one of these.