A work bench sounds useful and also Eric suggested it, but she'd like to find a good place for one in case the weird magic decides this is a permanent decision. "Eric", she calls out to him, "Can I move a workbench after I've made it?"

“Hit objects with your pickaxe to move them,” he advises. 

That is the stupidest way of moving objects she's ever heard of but okay. She makes a workbench on a bit of clear ground near Eric.

Now she has a workbench!

With the workbench and the small amount of wood she has remaining, she could make a chair or some wood walls. 

“Combine wood with the gel that drops from slimes to make a torch,” Eric hums to himself. 

Apparently she needs both of those to make a monster-free area, so she should chop down at least one more tree. But first she'll inspect the places the slimes where when she killed them, to see if there's any of the alleged gel present. 

There is! It’s in little blue spheres, very self-contained and tidy. There are also... coins? Copper coins, and one silver, shiny and round and perfectly smooth. 

Cautious poke at the gel with a finger to see if it will make a mess. Also, where did the slimes even get coins? Hopefully they just landed on some dropped ones and stuck to them, rather than, say, eating a person and digesting everything but the coins in their pocket. Now that's a pleasant thought, isn't it. Either way, she'll put the coins in the magic bag, in case she finds civilization and needs to buy things.

The gel does not make a mess. It is well-behaved gel. 

Now that she has gel, she can make three torches from one block of wood and one blob of gel. However, she does already have 25 of the things in her bag. 

Yeah, that can wait. First, she'll bag the gel and chop down a second tree. This whole thing feels a lot like the descriptions she's heard of video games. If she had ever been into video games maybe she'd have more idea what she was doing; right now the plan is something like "build a monster-proof zone, have Eric wait in it while she searches for other people or a way back home".

She now has a bunch of wood, in the form of a single cube of wood!

”Once you’ve constructed a dwelling, you should search for ores,” Eric recommends. “You can find some amazing things underground!”

"Eric, you're talking like I need to rebuild civilization from scratch. But you don't look like you've been living in the wilderness. Where do I find other people?"

"There are many different ways you can attract people to move into our town,” Eric says serenely. “They will of course need homes to live in."

"Why would I found a town instead of moving to someone else's town? I'm a researcher, not a, a mayor or an architect or whatever."

That one seems to stump him. "In order to smelt ore into metal bars for working, you need a furnace, which can be constructed using stone and torches," he offers.

"Ooookay." She will learn weird video game dimension metalworking after she has found some people who can pass the Turing Test. She takes off into the air, looking for signs of habitation. 

Once she's high enough, she may observe the following:

She's on an almost perfectly square island. There's impenetrable fog just past the island's borders on every side. The only sign of civilization is a ruined castle to her west. The biomes are an insane patchwork, snow and desert side by side with a tropical rainforest and a strange area of red stone and grass with unpleasant-looking things hopping around on it.

The air quality remains the same no matter how high up she is, but gravity starts cutting out about five hundred feet off the ground.

There's a woman flying by, with blue hair and wings.

Oh thank goodness, another magical girl. Hopefully one who knows where to find a town or something rather than a fellow stranded person, but at the minimum, she'll be company. "Hello there!" she shouts in the woman's direction.

The woman lets out a birdlike screech and hurls three dagger-like feathers at her.

Margaret's danger sense goes off as soon as the woman notices her, and she sees the feathers coming before they're launched. She stays well out of the way.

She's about to yell "Hey, I'm friendly!" when she realizes that the danger she's detecting is of the "environmental hazard" flavor like the slimes were, rather than the "hostile person" flavor she'd be getting off an actual angry magical girl or for that matter an angry cryptid. The entity throwing feathers at her isn't conscious. 

This is borne out by its movements; they’re strangely formulaic and exact, like the slime hopping once per second exactly. 

The harpy throws another three feathers in more or less the same pattern. 

She would have been delighted by the presence of another magical girl, angry or no; even a cryptid would have been a familiar sign of home in this alien world. But there's nothing to be gained from interacting with this thing. She flies towards the ruined castle instead. 

As she draws near, she sees an old man in a red hat standing in the entryway.

"You are too weak to defeat my master," he says without preamble.

"Bit of a weird question, but are you self-aware?" she asks. How ironic, she thinks, that she can only tell the difference when the entity in question is about to attack her.

"My master cannot be summoned under the light of day,” he comments. 

"Another robot, huh? This dimension stinks." She flies back to Eric and her workbench, for lack of a better base of operations.