Be very careful with the diaphragm, the stepped mica sounds much better than the flat replacement micas made today, the new replacements are too thick to sound as good as the stepped originals. Usually, a layer of thinned shellac is coated on each side of the bottom gasket, and then the diaphragm put on top of that, and the top gasket done the same way. I like to use rubber cement though because it can easily be removed, it offers softer surfaces and increases volume and bass response. I attach the stylus bar to the center of the diaphragm with sealing wax, shellac and African wax-based cement.
https://princetonsealingwax.com/ It is the oldest continuously operated business in our town. I use an alcohol lamp and dental tools to apply the wax to the center. Stratina, shellac or beeswax can also be used, but the sealing wax has worked really well for me, and for adhering the crossheads to glass diaphragms, and remounting recording still.