Java (OpenJDK 8), 200 190190 170 bytes
n->{for(char i=0,s[][]=new char[n][4+n+n];i<n;s[i][2+n+i]=92s[];i<n;s[-~n-i]=47,s[i][0]=i<1|i>ns[2+n+i]=92,s[0]=i<1|i>n-2?40:'|',s[i][3+n+n]=i<1|i>ns[3+n+n]=i<1|i++>n-2?41:'|',System.out.println("".valueOf(s[i++]s).replace('\0',' ')))s[i][3/2+n-i]=47;s=new char[4+n+n];}