Decreasing in pattern

Hi! I am knitting this cardigan linked below and am currently on the “Left Front- shape front slope” sections. It reads: keeping pattern correct, dec 1 stitch at the end of next and 2 following 4th rows, then on 5 following 6th rows. Continue straight until Left Front matches Back to start of shoulder shaping, ending with a ws row.

The 8 row repeating pattern is as follows:
1st row. K1, * p1, k1, rep from * to last st, p1.
2nd row. * K1, p1, rep from *
3rd row. p1, * k3, p1, rep from * to last 3 sts, k3.
4th row. * P3, k1, rep from * to last 0[3:3:2:2] sts, p0[3:3:2:2].
5th and 6th rows. As 1st and 2nd rows.
7th row. k1, * k1, p1, k2, rep from * to last 3 sts, k1, p1, k1.
8th row. * P1, k1, p2, rep from *

Firstly, how should I do the decreases? Just by k2tog? And secondly, how do I keep the pattern correct after? Would I begin row 5 after the first decrease with a K1 as usual, or now with a P1?

Any help massively appreciated!!!

Welcome to the forum!
You can use either a k2tog for a slant to the right or a ssk for a slant left if you’d like. Try them out on a small swatch to see which you prefer where.
You’ll want to maintain the pattern as set in the previous rows. That means you’ll need to account for the decreased sts. Either look at the pattern and figure out how to maintain the column alignment on the next stitch or subtract the decreased stitch from the pattern row.
If your decrease is at the beginning of row 5 for example you might k2tog that first K1 and the next p1. Then the next stitch would be the k1 in the first repeat: K2tog, k1, * p1, k1, rep from * to the last st, p1.

This is a good article on keeping in pattern while decreasing:

It may also help to make your decrease one stitch in from the end if that isn’t too confusing. It’ll make seaming easier because you’ll have that edge stitch. Same rules apply about maintaining pattern and accounting for the stitches used in the decrease.

Maybe this pattern?

Thank you for your reply! That makes sense about whether you want to k2tog or ssk. I understand how to keep it in pattern on the row I am decreasing, the part where I get confused is on the subsequent rows since there will now be one fewer stitch than before. Do I start the rows as normal or do I have to start from a different point in the row?

You’ll have to account for the decreased stitches. Just as with the decrease row itself, on subsequent rows you need to look to the previous pattern rows or subtract 2sts from the pattern row to account for the sts used in the decrease.