To begin, make sure the fruit you will be using is clean, and free of any debris like twigs and leaves. Jelly can be made out of literally any fruit, from apples, to kiwis, to raspberries. Simply place the fruit in a colander, and run some cold water over it. You can also use your hands to rub the fruit while holding it under a stream of water, to help dislodge any soil or dirt. Remove any bruised or rotten fruit, as this will spoil the taste of your jelly.
Once the fruit is clean, proceed to put it in a stainless steel stock pot, and use a potato masher to crush the fruit, and release the juices. Do not bother to pick out any seeds at this point – simply mash it all up, and add in a small amount of water, which will prevent the fruit from burning as it heats.
Next, put the pot containing the crushed fruit on the stove over medium heat, and allow the fruits to heat up until their juices begin to flow. Heat it gently for some time, stirring occasionally to help the process along and to ensure that the fruit does not stick to the bottom of the pan and burn.
Once all the juice has been released, turn the heat off, and take the pan off the stove. Let it sit for a while, to allow the fruit juice and pulp to cool – do not attempt to work with scalding hot fruit juice. Once it becomes lukewarm, or reaches room temperature, move on to the next step.
Line a large bowl with a large piece of cheesecloth that has been folded twice or thrice, to create a number of layers. Make sure it covers the bowl completely, with the corners dangling down the sides of the bowl. Once this is ready, start spooning the crushed fruit mixture onto the cheesecloth. Fill it up, but make sure you leave room at the edges.
Then, bring the four corners of the cheesecloth together, and tie them up with strong thread, to create a bag. Once it is securely closed and tied, hang this over the bowl, allowing the juice to drip down. However, make sure you hang it at a distance, leaving room for the juice to accumulate without the bottom of the bag touching it.
Once the juice stops dripping from the bag, squeeze it one last time to extract any last drops of juice, and then discard the bag. Your pure, seedless fruit juice is now ready to be made into jelly.