I will show you how to build a Pocket Rocket Stove.
If you don't know what a rocket stove is, have a look at "rocketstoves.com" or search at Youtube where there are tons of very good videos to get inspiration from.

Step 1: Material List

Materials needed:
1x oval bucket with lid
1x stove-pipe 120mm x 1 m
1x stove-pipe 130mm x 50 cm
10l hydro clay for hydroculture-plants
2,5 kg chamotte mortar

Everything costs about 35 EUR

Tools needed:
hammer (optional)
oil (optional)
marker pen
drill
metal scissors
scraper
bucket (for mixing the mortar)
bucket with the same shape as the bucket for the stove but slightly smaller
plastic bag
water

Step 2: Mark the Holes

Set the pipes on top of the lid and draw around them with the marker. Then drill a hole in the middle of each circle.

Step 3: Cut Out the Holes

Make star-shaped cuts in the lid. If your scissors don't fit in the hole you can enlarge it with a spiky hammer. Then bend the triangles down, so the pipe fits into the hole. Cut as many triangles as possible (more than shown in the picture). The smaller they are the better you can bend them and the better the pipe will fit.

Step 4: Insert the Pipes Into the Holes

Insert the pipes in the holes as shown in the second picture. The wood feed should be about 4 cm above the bottom.

Step 5: Make the Bottom of the Stove

When you have finished the lid you start with the insulation of the stove. It helps to keep the heat in the stove to make it more efficient and it protects the thin metal bucket from the heat and increases its durability.

Mix the mortar with water so it has the consistency of ketchup. Fill the bottom of the bucket with hydroclay ( about 2 cm high) and then pour the clay pearls into the mortar. Mix it well and pour it back into the bucket.

Step 6: Make the Stove-walls

Now take the smaller bucket and place it inside a plastic bag to protect it. Apply some oil to the outside of the bag, so the bucket is easier to remove afterwards.
Again, mix mortar and clay pearls. Then insert it into the stove and fill the gap between the outer bucket wall and the inner bucket with the mortar-clay-pearl mix. Compress the clay-pearls with a stick to prevent air bubbles in the wall. Let the mortar sit for at least 24h.

Step 7: Remove the Inner Bucket

When the mortar is dry, carefully remove the inner bucket. (The photo was taken after the first use)

Step 8: Finished!

Now put the lid back on the bucket and you are ready to start the fire. And voila! Smokeless, efficient fire and cozy warmth for sitting outside even in the cold season.

Step 9: Conclusion

After several months and using the stove a couple of times I can tell you this:

The draft often starts in the wrong direction i.e. suction through the cimney. You can prevent that by blowing into the filling hole or by starting the flow by pouring some flamable liquid down the chimney and light it.
The filling hole gets clogged easily by the ashes or coals and it limits the draw
the thin metal of the bucket gets brittle after a while and because of the steel is covered with zinc its everything but healthy what comes out of the chimney on the first fires

At least it was fun to build and I learned a couple of things, but definetiv better invest you time in building a REAL rocket stove.