Slugs will be around anytime you provide a good, healthy soil that is well endowed with organic matter and is propely mulched since that creates the conditions that slugs really like to live in, a cool, moist environment with ample food nearby. If the slugs are outside of the bed the plants they like are growing in the copper strips could keep them out, but if they are already in the soil n the bed the copper strips will be an expensive, and useless, attempt at control.
I find that I have less trouble with slugs when the mulch is quite heavy, apparently they have ample food in that mulch and leave the growing plants alone. Saucers of stale beer can be a less expensive method of control and encouraging toads and garter snakes to hang around the garden is another.

I've not used copper flashing around an entire plant bed, but going by my much smaller experience, it might work. Copper IS, by the way, an absolute deterrent to slugs.

I've used copper screen in the bottom of my outdoor containers to keep the potting mix in and the slugs out. I've also trimmed the outside of containers to prevent slugs from climbing in and helping themselves to whatever I may be growing.

Watch what happens when a slug touches something copper, and you'll see for yourself! It's almost fun!

An electrician I know would bring me scraps of copper wiring that I would make into a circle and lay around my hostas. Worked very well. It all gets recycled now so, alas, no more scraps.

tj

Slugs & snails can "loop" over a one-inch wide band. To be effective, it should be 4 inches. Then you have to monitor for any "bridges" -- plant material hanging over the fudge which can provide a detour and/or shortcut.

hehehe -- "plant material hanging over the fudge..." I meant "over the edge!" (spellers; aren't they wonderful?)

Thank you all, this post has been most educational. I did not think that slugs were actually in the soil. I thought they emerged from under the logs nearby at night and went to dinner on my plants. Also, I did not realize they were so 'agile' as to arch over bariers. They have been chomping on my beans and tomato plants, but they cannot completely wipe them out, but the green leafy veggies will be easier. I think I will use some copper flashing it it's not too expensive, put down some pellets, and try the slug patrol each night. I have a neighbour who does that but I'm not sure of her success. Thank you all very much.
Northerner.

I like copper against slug. The only problem to make sure that soil and compost that we add don't contain eggs of slugs.