Ok my friends, i make a wall with a mix of estuco and chalk, and it ´s oK, for the rock road i usede the same mix, now how do you guys attach walls to the base, considerin that the wal i make is 15cm tall, Tanks

You have a couple of options depending on how much support you need. The best option is to drill small, matching holes into the base and wall, insert toothpicks into those holes and glue the wall to the base; this would give the sturdiest construction for my money.
Kyle

Thanks for the tip, i´ll try and see what hapen, i´ll sohw the results.