This is an easy to replicate terrarium that can be produced with cheap materials and very few tools, although higher end tools can be used to achieve cleaner and faster results
I chose a hexagon as the shape to base it on because it makes it easy to add additional boxes, such as a hydroponics herb pod. It's also reminiscent of honeycomb, so that's fun too!
The materials used were about 150cm of wooden plank (15cm x 1.5cm cross section) and around 0.2 square metres of clear acrylic. The majority pieces can be made using just a jigsaw, and assembly requires only a screwdriver and drill.
Step 1: Cutting the Side Panels
By constructing the hexagon from panels that overlap each other, all the panels can be identical, which avoids the need to have a longer top/bottom piece and shorter side panels. Cuts should be made at a 60° angle and both point inwards. If using a mitre saw, you can set the angle and flip the plank over each time.
Once cut, line the panels up against each other, and drill pilot holes through the end of one panel into the adjacent one in order to prevent splitting when the screws are inserted. For added safety I countersunk each screw hole before driving them in. You can use wood glue in the joins for added rigidity.
I measured the external wall length as 15cm, so the internal diameter at its widest point is 30cm, although unless very short plants are used, you won't be able to use the full width, so take it into account when choosing the size.
Step 2: The Back Plate
Place several short plank sections next to each other so that the whole area inside the walls is filled, then draw around the inside. Use a jigsaw or hacksaw to cut around the lines, and the shapes should fit perfectly within the frame. This will take away 1.5cm from the available planting depth, but you could always trace around the outside of the frame instead if the full plank width is required.
Wood glue may be sufficient, but I wanted the option to hang it on a wall, so I used an additional 2 screws per side for extra strength.
Step 3: Fitting the Acrylic Window
The acrylic front panel is necessary to prevent the soil and gravel from falling out. I used a rotary tool at a fixed distance to carve a shallow groove for the front panel to slot into. With a few coats of varnish it should be possible to create a watertight trough, although I chose to create additional acrylic panels to effectively line the entire bottom half of the hexagon with acrylic.
I didn't have any wood filler to hand so I mixed some of the sawdust collected from drilling the holes and cutting the back panels with wood glue, smoothed the screw holes over with the paste, then sanded them down once dried.
Step 4: Wall Mounting Bracket
The entire thing ended up being around 3kg when finished, so a pair of brackets rather than a single one would be a better idea.
I chiseled in a shallow recess for a 1mm aluminium plate with a keyhole cutout before securing it with epoxy and 4 short screws, none of which protrude further than the back panel, so the whole box will sit flush with the wall when mounted.
Step 5: Wood Stain
You can leave the wood in its original state, or give it a darker stain. I used a decking stain which helped to hide the different textures of the smooth wood and the rougher areas that were cut at an angle (Some thinner stains will show up much darker on areas that have been cut against the grain, so use a scrap piece to test first if you're unsure).
The surface was still slightly rough, so I also gave it a coat of polyurethane varnish to keep it smooth and shiny.
Once the varnish had fully dried, I arranged the acrylic panels and secured them in place with silicone sealant.
Step 6: Adding the Plants
How you fill the terrarium is up to you, though it's most common to use coarse sediment on the bottom and work up to finer grains (Pebbles, gravel, sand, soil), then add small plants with a low water requirement.
Make as many as you feel like and stack them, or display them individually!