Consider collecting all the recycled filter paper in your house. You can look for the scrap paper by yourself or ask your children to do this job for you. Kids usually waste a lot of paper and you can put all that to use by coming up with something which can be used by them on a regular basis.
Once you have a large amount of filter paper right in front of you, consider folding the paper in half from top edge to the bottom edge. Fold the paper in a way to create a horizontal crease. Unfold the paper now.
Fold the paper again from left to right. Again crease and fold. It is recommended to fold all corners of the paper into the centre so a small square is formed. Fold the top edge of the square inwards to connect to the centre crease. Repeat the same for the bottom edge. Crease and fold.
Always note the six horizontal creases that have been created as you open up the bottom and top edges of the paper. Let the left and right hand sides of the paper meet at the center by folding them inwards. This will results in a narrow and long shaped folding.
Consider forming a diagonal on the left side by folding the top corner over to the right. Crease and unfold. Repeat the same process for the right side of the paper while folding the top corner to the left. Repeat this step for the bottom corner of the paper.
It is advised to open the folds in the top corner very gently. As you open the top corner, it will be directed vertically. Fold the top corner at an angle right over the side of the filter paper case. Repeat the same process for the other side of the case.