I was goofing around in the net and noticed that many had problems combining Sims, death and flames.
Actually, I was trying to look for a way myself.

After few real-life hours of testing and one sim that died of old age before I managed to set him on fire, I found a method that seems to be quite fool-proof.

I do not know if there is a complete guide for this done already. I just want to share my trick, and maybe somebody will think it is useful.
For this method you do need Outdoor Retreat-gamepack.

First things first: You must build your trap of death. Choose a spot far away from your house.
Then build a room: It needs to be at least 2 squares wide and 3 squares deep, but not any bigger.

After that, pick a campfire from Outdoor Activities-department and place it in your room. It should take 4 squares of space, leaving you with 2.

Continue by choosing a carpet of your liking and placing it inside the room, also under the campfire. As, for some reason, you can place carpets in top of each other without cheating, I recommend to cover the room with thick layer of them. For a reason: If you have many of them in top of each other, the fire does not burn out before it reaches your sim.

One guide I was looking told to fill the room with "anything flammable". After filling the room with clutter, like curtains, paintings, chairs, boxes, folding screens and God-knows-what, I came to conclusion that it was waste of time and money. Carpets are all you need, and they actually work better alone than with junk everywhere.

At this point your pit of hell should look like this:



Noticed the small piece of floor which was left uncovered? You'll need it later.

Next thing to do is prevent fire from spreading. As it can go through walls, you can accidentally burn down your whole house (which I did). Also, even if another sim tries to put out the fire outside this one room, it will also put out the fire inside the room.

To do so, surround the room with a two square wide swimming pool. It's wide enough to keep the fire from spreading, and keeps other sims from ruining your perfect murder. Also, if you want to drown your sims, just surround this one with fence and it's good to go.

After completing all this the result should look like this:



Now, to get your sim inside this room, you got need to build part of the pool and wall after your sim is inside the room, or use a cheat.

Press SHIFT + CTRL + C and type "testingcheats true". Close the text window, press SHIFT and click on the floor, which was left uncovered earlier. (Clicking on the carpet wont work.) Then choose "Teleport here".

Now you can get to action. I usually follow these steps, but, as I'm not sure if they have effect, I don't say they are must.

1. Click on the campfire and choose "Light"
2. Click on the campfire and choose "Add firewood" for couple of times
3. Click on the campfire and choose "Play"
4. Repeat if necessary

And the result will be this:



Yes, there is Grim Reaper standing behind her.

I have tried to cause a fire by bad cooking or with fireplace (actually, three of them), but campfire was definitely the most effective way. It can take a while to work, or it may work almost immediately. But for me it has always worked. As it was not mentioned in any guide I was reading myself, I wanted to share this with you. And if everything goes according the plan, you will be eventually rewarded with sight like this:



Thank you for reading, and feel free to comment, ask and criticize!

KILL IT WITH FIRE!

Thank You.

Ooh, a crematorium for live people.