Place items on backpack and character.

[molten gate]

Place items like weapon magazines, first aid kits, water bottles/canteen, lightweight camping cook set (hint hint), rolled up tent, fishing rod, wood axe, compass, cellphone, forward facing flashlight (on chest) and handheld radio (belt) on backpack, waist or chest with click on item, "Place on character/backpack" option. Requires Velcro, needle and thread. Found/crafted MOLLES can be used without Velcro. Doesn't require crafting table. Military backpack and SWAT vest have more slots. Camping Backpack and standard clothes have less. Items placed on chest slightly reduces carry weight due to optimized weight distribution.

• School bag - 2 slots
• Gym Bag - 3 slots
• Camping Bag - 6 slots
• Military Rig - 8 slots
• Standard Clothes - 2 slots
• Fireman's Jacket/Police Shirt/Swat Vest - 3 slots
• Military Vest - 4 Slots (Stacks with Military Rig + Tactical Belt)
• Normal Belt - 2 slots
• Toolbelt - 5 slots and storage. Tools, nails and screws only. Required tools aren't needed in crafting table if they are attached to toolbelt. Mini Sledge uses 2 slots.
• Tactical Belt - 3 slots
• Military Belt - 4 slots

[mortal cloak]

This has some cool ideas on it. I like the idea of not needing a creating table for things that already have molle, but think that would be best for things that don't. In the military people have made molle webbing on things in the field too.

As for other "slots" I could see some pre-made ones that AREN'T universal. For example, my Adidas draw string gym bad comes with a water bottle pocket that could be used for many quick access things, but wouldn't support a skillet, a sleeping bag, or a weapon.
This could lead to different bags having variants that include built in "slots" that could be blocked based on size from use of other items.

Some "slots" could be incredible easy to make. For example, you could make a hatchet holder on the side of a bag simply by sewing a horizontal loop onto the bag small enough for the handle to fit but not the head to go through. Could add a verticle one that is snap or velcro to secure it. This could be a way to create some slots, but also create LEVELING to the slots.

Clothing themselves shouldn't come with slots for the most part. Carpender pants would make sense as they have between 1 and 3 loops/hammer pockets on them. However simply a T shirt with no pocket and athletic shorts wouldn't have a slot.

Another distinction for "slots" could be affixion points versus insert points. for example, holsters, sheets, loops, hammer pockets, etc. are insert points as the handle of something or the body of something goes down into a segregated space in order to hold the item. Things such as Molle wedding, Velcro, slide pin, stretchy, spandex, strap, etc, are used to fix something to another. The main difference in use would be load bearing on the means of holding, weight limit on the structural being used to hold, movement buff based on the location of the weight, etc.