Use a rpi as a wireless router?

[Helpful Tech Witch]

I have a raspberry pi as a wireless router but I can t figure out how. Itll be plugged into my pc when needed and then only one thing will be connected to the network it provides

 My rpi is a pi4 8gb with arch
Ive seen a couple things in the arch documentation for how to do it, but it doesnt make sense to me tbh. 
It seems simple but idk how to do it...

[Ralphred]

It's not particularly hard to do, but I wouldn't recommend it, the wireless is pretty meh.

You'll need:

• hostapd provides "Wireless access point" functionality (easy to set up)
• dhcpd will hand out IP addresses on the wireless lan (or dnsmasq if you like)
• iptables will do the firewalling and NAT* (probably the most reading to understand and get it right)
• some general networking stuff (nothing out of the ordinary, turn on packet forwarding, make sure the routes are right etc)

*There is a way to do it with bonding, but it's not something that works properly with systemd-networkd without post boot fondling (plus the documentation is both wrong and shitty).

[Helpful Tech Witch]

27 minutes ago, Ralphred said:

• iptables will do the firewalling and NAT* (probably the most reading to understand and get it right)
•  

without outside network access, i shouldn't need either of these right?

[Ralphred]

You'll need NAT (without bonding) but it's one line to make it work.

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

assuming your PI's NIC is called eth0. The rest of the default policies are ACCEPT anyway, so there is nothing to do unless you want to.