It's easier to get detailed cuts if the copper tape is attached to final surface instead of slick backing paper on which it comes in the roll.

Make at least 1 cm overlap for each slice of copper tape

Cutting copper tape requires very little force. If you set the cutting force to minimum it should cut the copper tape without cutting OHP film even when blade depth isn't properly adjusted.

Glue on the back of copper tape with thin traces doesn't make a reliable electric connection. Sometimes it's good enough, but not always. Join the parts of tape using small dots of solder. Not needed if you were able to source sufficiently wide copper tape or sheet of foil.

Somewhat finicky since the copper is in the middle with plastic film on the outside. Lightly tin the ends of traces but don't apply too much solder. Having a bump will make it harder to align the traces, also if you try to squash it while solder is molten it can squeeze out shorting multiple traces together.

Don't try to make too much overlap. 1-2mm is enough. Longer tinned section means longer part with weakened glue which can lift off and go sideways ruining everything.

Be very careful not to lift any traces. As you solder the glue holding copper tape will loosen up.