Unfortunately I didn't really think about it until the cooking was done, so I only have pictures of the post-cooking steps.
Step 1: Ingredients and Recipe
1.5 cups mango pulp/pureed mango
1.5 cups pureed strawberries
2.5 cups sugar
1 tbsp butter
6 fl oz liquid pectin
My grocery store doesn't currently have fresh mango, so I used cut, jarred mango. One 24oz jar yielded roughly the 1.5 cups I needed. A 16oz container of fresh strawberries gave me my 1.5 cups of pureed strawberries -- at least it did after I threw out several for being overripe.
Pectin can usually be found either in the baking aisle -- usually in the same area as unflavored gelatin packets -- or possibly with canning supplies if your grocery store carries them.
I'll detail the process a bit more in a few steps, but in case the original site is down or moved, I'm copying the complete instructions here verbatim.
1. Prepare an 8x8-inch square pan by lining it with aluminum foil or parchment paper and spraying the bottom with nonstick cooking spray.
2. Cook mango pulp and sugar together in a medium saucepan over low heat until they form a very thick syrup. Depending on the thickness of your pulp, it will take between 30 minutes 1 hour. The syrup should thickly coat the back of a spoon or spatula.
3. Once the syrup has thickened enough, add the butter and cook for 3 minutes more, stirring constantly.
4. Remove from the heat and stir in the pectin while hot. Pour immediately into prepared pan.
5. Allow to cool to room temperature. Cover pan with foil and refrigerate overnight until set.
6. Once the candies are completely set, cut them into small squares with a knife dipped in water. They can be rolled in granulated sugar or left plain. The sugar makes them easier to store and stack, as it prevents them from sticking together.
7. Candies can be stored in the refrigerator in an airtight container for 2-3 days.
Step 2: Tools
Food processor or blender to puree the fruit
8x8 or similar pan (I used a 8x6 to end up with a slightly thicker final product)
medium saucepan -- You'll want something that conducts and holds heat well. Thin, cheap pans won't heat evenly and you may end up burning the fruit/sugar mixture in spots. Currently I'm using a 1.5L Corning Visionware glass saucepan that is most likely from the 70's.
And some minor other items:
aluminum foil or parchment paper
nonstick spray or similar
metal spoon or similar to stir the mixture -- do not use a wooden or plastic utensil. Whatever you use should be heat resistant to several hundred degrees Fahrenheit.
wax paper and container to store the finished candy in
Step 3: Cooking
Measure 1.5 cups of the puree into the saucepan. Add the 2.5 cups of sugar to this and mix it together.
Put the saucepan on the stove on a low or medium-low burner. Stir constantly at first until it looks like the sugar is completely dissolved. Continue to cook the mixture, stirring occasionally, until it forms a thick syrup. My strawberry ones were cooking for about 35-40 minutes and they turned out much softer than the mango ones (which I cooked for about 50 minutes). I intend to retry a strawberry batch with a longer cooking time at some point.
While it's cooking, line your pan with parchment paper, aluminum foil, or something similar to ease candy removal later. You can also spray it with non-stick spray, though this is not absolutely necessary.
Stir the butter in to melt it and continue to cook for another 2-3 minutes. Remove the mixture from the heat and stir in your 6oz of pectin completely. Immediately pour the mixture out into your prepared pan.
Let it cool down to room temperature. Cover it and allow to set completely. The recipe I followed suggests doing this in the refrigerator, however I've had bad luck in the past with jelly and gummy candies not setting properly in the refrigerator, and other sites I checked suggested simply covering and leaving out overnight. This is what I did with the strawberry ones. The mango ones were left covered and out for about 8 hours before I judged them firm enough to continue.
Step 4: Cutting
Lift up your paper/foil liner to remove the candy from the pan, then flip it over onto a cutting board and peel the liner off the candy.
Cut the candy into 1 inch or so squares -- or whatever shape you want really.
Once it's cut you'll move on to sugaring.
Step 5: Finishing
I layered the pieces in a small plastic container by placing a piece of wax paper between each layer of candy to further prevent sticking.
As long as you have a good airtight seal, these should keep for several days in the refrigerator.
Step 6: Final Product
At the time of writing this it's been 3 days for the strawberry and 2 for the mango. They're doing okay in terms of keeping, however they have gotten a bit moist/sticky on the surface and have managed to mostly dissolve the sugar coating. I'm not sure if this is indicative of an incomplete set (either from a too-short cooking time, or a too-short set time) or if this is due to my containers not being sealed well enough resulting in added humidity from the refrigerator getting in and disrupting them. In any case, they do not appear to actually be suffering from this, rather it's just a cosmetic and stickiness issue.