Geez man. I'm going disagree with him strongly on this. I recommend you have the edges routed. If you choose to scrape you have to be very even and if you make the surface sloped or round edges you risk air intrusion into the seam or the seam isn't square. might look okay but can fail prematurely.
Go to local plastic shop and get cheap scrap. Practice. Weld on4 is ok. Better 93% methylene chloride 7% glacial acetic acid. Longer work time stronger bond. If you use Weldon 4 don't wait 2 minutes like he says in the video. It will already be setting and the pins will likely leave bubbles and a gap for air intrusion.
