I have done it a few different ways, but this seems to be the best because it can be reversed in an instant should you want to sell the machine......first unplug machine, take out the 2 screws that hold the control panel in place, and tilt forward....now you have 2 switches, the one near the front has to be unscrewed and wrap the ends with electrical tape, leaving the screws in place for later use, DO NOT wrap tape around the little plunger that pushes in(usually red or white), and tape this switch off to the side.....now take the rear switch remove the screws and wrap electrical tape around and over the plunger while holding it in, tightly, and re-install in place, now reassemble the control panel, and your machine will now operate with the lid open or closed.....
if you want to re-sale the machine you can always just remove the tape and put everything back the way it was........sometimes theres a little fuse attached to the switch mounting plate, if you don't do this correctly it will POP this fuse....cheap and easy to replace if you do, been there and done that!