Here's how you can make a form box to make a silicone mold for a good sized concrete planter. Use cheap, easy-to-find materials to make the mold form. This is how you can make copies if objects from your home to use as molds for your planters or any other concrete items.

--Timestamps--
00:00 How to Make a Large Concrete Silicone Mold For A Planter
01:47 Measure And Trace The Pieces For The Block Mold Form
03:54 Attach The Sides To The Base And Secure The Glass Bowl
06:26 Create A Hole For The Planter To Drain
07:00 Cast The Silicone For The Large Concrete Mold
09:50 Demold The Bowl From The Large Concrete Silicone Mold
10:43 Cast The Concrete For The Large Planter
13:35 Remove The Planter From The Large Concrete Silicone Mold
14:32 Final Step: Sand Any Sharp Edges and Pot Finished Piece with Cute Succulents!

Check out the detailed written tutorial on my website for some more information.
https://artsyprettyplants.com/diy-lar...

Materials:
Silicone mold making material parts A & B-platinum: https://artsyprettyplants.com/refer/p...
Mold making material, use this code for 10% off: ArtsySphere10

Large glass bowl
Pink foam insulation board 2’x2’: https://artsyprettyplants.com/refer/f...
Craft knife with whittling blade: https://amzn.to/36BsGI1 whittle blade: https://amzn.to/3DS7Wv6
Hot glue gun and extra glue sticks: https://amzn.to/3b6VVUD
Duct tape: https://amzn.to/30OncKO
Jumbo straw: https://amzn.to/317GCsj
Cooking oil spray
Silicone mold making material parts A & B-platinum: https://artsyprettyplants.com/refer/p...
–use code: ArtsySphere10 for 10% off
Permanent marker
(2) big plastic pitchers
1 large plastic container or bucket for mixing the silicone
Oil-based clay –may not be necessary: https://amzn.to/2YJ0H71
Big plastic spatula or spoon
Utility knife: https://artsyprettyplants.com/refer/r...
Putty knife or chisel- something for prying
Needle-nosed pliers: https://amzn.to/2UkPzuE
Dish detergent