@Adam_S by what we have seen so far I would do the following:

First you need to let the layout.blade.php view know that it has to accept a variable, so you should modify the <title> element inside the <head> of the layout.blade.php file like this:

<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <script src="https://cdn.tailwindcss.com"></script>
    <title>{{$title ?? 'Document'}}</title>
</head>

Notice how the <title> element is different from the one you had before.

By the way, writing this:

$title ?? 'Document'

should be equal to:

isset($title) ? $title : 'Document'

The first is called null coalesce operator (https://wiki.php.net/rfc/isset_ternary) What it does is it first checks if the variable $title is set and if it is it automatically assigns its value. If it is not set, it will assign the value 'Document' as a failsafe.

You can check that now whatever page you navigate you will see the title in your browser tab stating "Document"

Now that we have allowed the layout.blade.php view to accept a $title, we can go to the job.blade.php file and pass the variable $job to the layout.blade.php view this way (look at the second line of code):

<x-layout>
    <x-slot:title>
        {{$job['title']}}
    </x-slot:title>

    <x-slot:heading>
        Job
    </x-slot:heading>

    <h2 class="font-bold text-large">{{$job['title']}}</h2>
    <p>
        This job pays {{$job['salary']}} per year
    </p>

</x-layout>

I used

{{$job['title']}}

since we already have the $job variable passed to the job.blade.php view, but you could just replace it with

{{$title}}

since it is what you passed from the web.php file.

Obviously my code will just replace the title tag with the job name and not with the entire phrase you wrote. Anyway I would just suggest you to use

{{$job['title']}}

and don't add data manipulation inside the web.php file, do it in the view instead. You could just rewrite the job.blade.php file like this:

<x-layout>
    <x-slot:title>
        Selected job: {{$job['title']}}
    </x-slot:title>

    <x-slot:heading>
        Job
    </x-slot:heading>

    <h2 class="font-bold text-large">{{$job['title']}}</h2>
    <p>
        This job pays {{$job['salary']}} per year
    </p>

</x-layout>

I hope it was clear, it's midnight where I live and I really need to sleep and I'm also not that good with php/laravel yet XD

One more thing, you could also pass the 'title' as an attribute to the <x-layout>. Like this:

<x-layout :title="'Selected job: ' . $job['title']">

    <x-slot:heading>
        Job
    </x-slot:heading>

    <h2 class="font-bold text-large">{{$job['title']}}</h2>
    <p>
        This job pays {{$job['salary']}} per year
    </p>
</x-layout>

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