This is the way that I do it and I am not dexterous but I do seem to get an evenly shaped cake out each time I use this method. It is a bit long winded for which I apologise.
The first thing I do isroll out a piece of greaseproof paper that will comfortably take the base of the pan you are going to use be this round or square. I then double it up and then fold it in half.
I then place the base out of the tin onto the paper and go round it in biro so that the template is marked.
I then cut out working from the outside unjoined edge cutting through both pieces of greaseproof until I have two circles.
I then repeat this procedure again so that I end up with four circles.
I then get a piece of string or wool and run this round the circumference of the tin allow about an inch longer and then cut.
I then use this piece of string to measure the length of the paper that I need to line the tin.
I cut this to the length of the string and then fold this in half.
I then fold up a good inch on the loose side of the paper (not on the fold) so that the top of the liner is joined
I then cut at good inch intervals as shown below along the edge that has been folded making sure not to cut beyond the fold.
We can then start assembling the tin I grease one of the circles and place this greased side down into the tin. I then grease the top and then press the second circle on top pf this. I then grease this again.
We then come to the long strip with the cut flap and grease this well - this is where things can get a little messy. You need to grease the long deep part and the cut flap as below. I always melt some fat in the microwave and then use a silicone brush for this purpose.
Once you are happy with the easement chop off any excess so that the liner sits as below. Then add another circle of greaseproof this time over the cut flanged pieces. Grease it well on top and then add the second circle. This helps to reinforce the base so that the cake once cooked does not fall out.
This completes the inner lining of the tin.
However, to keep the cake from catching you will need to wrap brown paper or newspaper round the outer edge of the tin and tie this with string.
Then cut a couple of further circle and cut a 50p sized hole in the middle of the paper. Once the cake mixture is in the tin this can then be placed on top to stop the top of the cake catching.
I hope this helps.