My sapling's roots are growing out the drainage holes

[Hairy Potter]

Hello, I am new to bonsai. I have been taking care of a magnolia sapling (gathered from a neighbor's yard with permission) for about 4 weeks now. It is planted in a "self-watering" container, and I water it through the hole at the bottom.

The aforementioned pot

This tree has been growing very rapidly! I detached the reservoir to clean out bugs and buildup, and I noticed roots growing out the bottom of the pot

Does this put my tree in danger? Do I need a bigger pot ASAP? How risky would it be to repot it at this time of year, at this tree's age?

Here is a full picture of the plant and its pot(with reservoir attached). Tape measure for scale

I am very new to bonsai, and any information you can give me will be very appreciated! if you need more details, please tell me and I will be happy to provide them. I am a little over my head here, and I'm uncertain about the next step in the process of growing a bonsai, but those questions can wait for another day. Thank you, and I'm looking forward to learning more about this art

[imafan26]

Your tree is still young, not really a bonsai yet. Just a starter. You want the plant to build up the stems before you can shape them. I would just root prune and keep it in the same pot. It has a lot of growing out to do yet.

[Hairy Potter]

Thank you, I appreciate you taking the time to answer! This tree definitely still has a lot of growing ahead! It seems very healthy, and it's growing lots of new branches, which I hope will cause the trunk to thicken up some. I will look into root pruning. Should I change the soil as well? It was potted in a standard potting soil with a bit of mulch mixed in. I have read that bonsai need a different soil, but I'm unsure of how to properly replace the soil, or even if it is necessary for a young proto-bonsai.

[imafan26]

Since it is still growing out in a nursery pot, nursery soil is fine. If the soil is still good, I just root prune. and inch of the sides and I take a bit more off the bottom depending on how thick the roots are.

[Hairy Potter]

Do I need special tools for this or can I just use scissors?

[imafan26]

I use a bread knife I got from a thrift store. Serated knives make good cuts. Scissors or pruners will work. Just be careful. On the bottom that you only cut excess roots and not the main ones. On a pot bound pot I usually have a ring of roots at the bottom of the container.