ruby, 65 bytes

Result

AC

Duration

1061ms

Code [DL]

n=gets.to_i-2
m=gets.to_i
puts ?**m+?\n+"*#{" "*(m-2)}*\n"*n+?**m

stdin

16
36

stdout

************************************
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
*                                  *
************************************

stderr