The solution would be like this for this specific problem:
A∫0E.ds=qϵ
σ = q/A
E.2A=q/ϵ and E=q/2A∗ϵ = σ/2epsilon
I am hoping that this answer has satisfied your query and it will be able to help you in your endeavor, and if you would like, feel free to ask another question.