How would I go about making this: https://www.ebay.co.uk/itm/135-degree-Corner-Edge-Molding-trim-dollhouse-1pc-23/192652458710?hash=item2cdafb3ad6:g:bjsAAOSw~4BcAIqC I.E 135 / 45 degree wooden trim, how do I make this firstly with power tools then with hand tools?
With power tools you'll want to use a table saw. Rip thin strips off a larger piece of stock, tilt your blade to the appropriate angle for the miter (22.5 degrees in this case), set your fence for the desired distance from the point to the edge, and rip them to width. Since this is so small you'll probably want to set up featherboards and/or hold downs.
For hand tools you'd basically do the same thing but with a hand saw and a plane. Joint one edge of a larger board flat, then rip a strip off and plane it to thickness. Then joint one edge square and layout your angle on the end of the board referencing that square edge. Use a marking gauge to mark a line on both faces based on that layout and plane to the lines.
To glue them together I'd start by cutting a few blocks at the desired total angle (135) and cover them with packing tape. Then run a strip of blue tape along the outside of the joint, add some glue, and fold them together. Clamp (or tape) the blocks with the tape on them every foot or so to the inside of the work piece to make sure the angle is correct, and add tape to hold the rest of the glue line together.