myString = malloc((int) sizeof(STRING*) * 5);
for(int i = 0; i < 5; i++)
    myString[i] = str_create("");

myString = malloc((int) sizeof(STRING*) * 5);
for(int i = 0; i < 5; i++)
    myString[i] = str_create("");
	
for(int i = 0; i < 5; i++) {
    myString[i] = malloc((int) sizeof(STRING*) * 5);
    for(int k = 0; k < 5; k++)
        myString[i][k] = str_create("");
}

STRING** mystring;   //note the DOUBLE-'*'

myString = malloc(sizeof(STRING**) * 5);
for(int y = 0; y < 5; y++)
{   mystring[y] = malloc(sizeof(STRING*) * 5);
    for(int x = 0; x < 5; x++)
    {   (mystring[x])[y] = str_create("");   }
}

// and you need to use the "(mystring[x])[y]" format to access them

// because the format "mystring[x][y]" only works with pre-defined global arrays