give a simple way to solve the gaussian surface
Consider a Gaussian surface such that
(1) It include all the field lines emitted by the charge particle enclosed within the surface.
(2)The field should be parallel to area vector at each point on the surface.
(3) Electric field should be constant on the entire surface.
After this
Use Gaussian law
Flux = Q/ε0.
Then we can also apply
Flux = E.dS = E* area of Gaussian surface
on equating both we can solve for any unknown quantity.