If you can find any conducting gasket that will work, but watch out for problems in arcing if you have high power inside your oven, see below.
One real problem about the location of the gasket as shown in your drawing, if you put a short 1/4 wavelength down a slot like you have it (and you are close to 1/4 wave or 1.2 inches length), it'll make an open circuit with high voltage at the slot edge on the inner edge of your oven slot and you may accidentally create a point for arcing. You don't want an arc generator, it's noisy and can cause bad stuff, fires, etc.
Standard home use Microwave oven doors are 1/4 wave open circuits, i.e. when you close them, they don't short circuit the door to the oven, they leave a gap at the door perimeter that's specifically 1/4 wave (electrical length) so that when current reflects off that edge (it's an antenna like mismatch with air that makes the reflection), that reflected current heading back into the oven recombines with the original field inside to minimize the voltage at the gap.
A quarter wave short is exactly the wrong distance, it interrupts the current at the door gap point inside your oven and will make a large voltage at the gap and set you up for ugly arc's possibly (power dependent). You want your short at closer to 2.4 inches down the gap of your door closure, not 1". 2.4 inches would be a half wave short, which reflects as a short and minimizes the voltage at the gap on the inner part of the oven.
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