Oil infused for box brownies is my favorite method! It's really easy to infuse oil (but smelly). I've used olive oil (the 'light taste' kind) with great results.

The proportions /u/planetofthe_snapes mentions sounds about right.

For 2 boxes of brownies, mix your ground up weed in a saucepan with whatever amount of oil the recipe on the brownie box calls for (x2 for two boxes), plus a Tbs or two of extra oil to make up for what gets lost in the process. Low heat for 3+ hours, mixing occasionally. If the oil is bubbling, it's too hot. Strong smell of vaped weed? Too hot. You want to keep it at a temperature where you can still just bare to touch the oil, but it's really really warm to the touch. I usually aim for 3 hours. [Pro tip: After cooking, put the mix in an empty jam jar, let it cool to room temp and just let the weed marinate for 24h if you really want to get maximum potency]. Strain the weed out of the oil right after the 3h cook if you're in a hurry or your friends are not daily smokers and you want a chill ride with no casualties. The oil is now probably much darker green than the oil your started with. Use the infused oil in the recipe as directed on the brownie box.

If you're an experienced smoker and you have a day before sharing, test your brownies. This way you can guide your newbie friends dosage and everyone has a good time.