Hi @jbandhs,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
Assuming you are going to mount the timber to the top of the garden beds, so that it is not in direct contact with the soil, then you'll need to use a timber that is suitable for above-ground outdoor use. This can be a hardwood such as merbau, or a treated timber such as H3 pine. The timber used in the photo is treated pine and it is what they typically refer to as a batten, which is around 40x40mm.
In some areas, there are H3-treated pine battens of a similar size, but they are not everywhere, so I couldn't send you a direct link. If you give your local store a call, they may be available, but I can't guarantee it. If they are not available, I'd suggest using this 42 x 42mm Merbau Pre-Oiled Solid Screening.
To join the timbers together, you would use 75mm Galvanised Timber Screws, predrilling the timber with a suitably sized drill bit for your screws. If you used these specific screws, you could use a 3mm drill bit.
To keep birds out and let pollinators in, chicken wire is a good choice. You can attach it to the timber using Galvanised Staple Nails, which are just hammered into place.
The last thing you'll need is some hinges. Being outdoors, they will need to be rust-resistant, so you will need either galvanised or stainless-steel hinges and screws to attach them with.
You'll then have to cut your timber to length using a saw. A mitre saw would be the best option, a circular saw would be good, but everything is achievable with a hand saw.
The design is relatively simple, just using a series of rectangular panels, with corner bracing. You can tailor this design to your needs fairly easily, but if you need a hand with this, please provide us with some measurements for your garden bed, and we'd be happy to help.
I hope this helps. If you have any further questions, please don't hesitate to ask.
Jacob
