Everyone has their own way to make tanks. I agree with Barrie. After cleaning I lay the bits out like an exploded drawing on a flat surface and then put all the glue on. Go right around the top edge of the base and on the edge of the front and back (where the pieces will come together). Then as Barrie said, back, end, end and front. You can use masking tape but sometimes it is hard to clean off after a weak so I prefer PVC insulation tape. After you have made a few hundred you will develop your own preferences. Squeeze the joints tight to exclude air bubbles as you tape,then run a fillet round all the inside angles and smooth off. The temptation is to use a lot of glue on the first one. You don't need much and it looks better as well.