read this first and get to know what you are doing. there are tips that will help prevent failure due to contamination.
this first link will provide detailed instructions on brown rice flour or BRF spawn techniques.
https://mycotek.org/index.php?threads/brf-tek.122/
and here is a detailed instruction on how to make a mushroom fruiting chamber this is called a Shotgun Fruiting Chamber. or SGFC for short
http://freshcapmushrooms.com/learn/how-to-build-a-sgfc/
Do not alter any of the details in the directions!!!! except for the following details which i have found to work well:
An air pump can be used by sliding the pump's hoses through two of the holes you will have drilled and leaving the pump on the outside of the chamber. Use airstones to diffuse the air into the water. Place the air stones in a plastic cup and fill with sterile water. change the water with fresh sterile water once a week and top it off periodically throughout the week. This will spritz water around in your chamber. i have noticed mushrooms will produce more on the side facing the bubbling water. This is clearly because they enjoy the moisture.
You can cover all of the holes above the perlite line with micropore tape to prevent bugs from entering. If you arent using an air pump you may still do this but will likely have to provide extra fresh air exchange.
THIS IS A MUST!!! raise the fruiting chamber off of the table it is on by placing upside down cups under each corner. this will allow fresh air exchange through the bottom and excess moisture wont build up into standing water. you do not want standing water in the chamber. but you do want 100% humidity and frequent fanning. you will learn what works best for you as you practice.
i recommend making new spawn jars constantly so you have room for error and to find niches that work well FOR YOU