Wash the oranges well and with a peeler take out the peels of 4 lemons, if you don't have one use a knife to peel but try not to cut much of the white pith as it's bitter, so this peeler makes by life easy and I get a long strand of peel, which later you can make it just like that long or cut in small 2- 3 inches length, with knife peel it vertically into thin strips.
Slice the other two lemons, not too thin nor too thick. I got 15 slices from the two oranges

Blanch the peels to get rid of the bitterness of the white pith. I did it twice, as my peels were quite thin and did not have much white pith. If you have more of white pith do it 4-5 times.
Blanching the peels: in a pan take water and peels, the peels should be submerged in water. Put on the stove and bring to a boil, once it starts boiling strain the water and add fresh water and repeat the process.
You don't have to blanch for the lemon slices.

Now mix sugar and water and bring to a boil. Once it starts boiling add the slices and the peel and simmer till the peels becomes glossy and fairly translucent. I kept the peels fairly long.

Once done with the help of a tong or fork take out the slices and the peels (if you don't like it to be covered in sugar) and keep it on a drying rack and then strain the rest of it. Take out the peels from the strainer and put it in a plate of sugar (take enough sugar to comfortably coat or dredge your peels). Toss and evenly coat all the Candied peels and put it on a wire rack to dry.

Once dried keep the candied slices and the candied peels in an airtight container.
Use the Lemon slices to decorate/ garnish / top your cake and dessert or have it just like this.
The peels you can add to your Plum cake, fruit and nuts cake along with Candied Orange Peels or on in your Lemon cake (for this I don't dredge it sugar).

The sugar coated Lemon peels you can have it like a candy or dip it in chocolate, lemon and goes also goes well in flavour.
You can garnish your cupcakes with it too.

Candied orange peels and candied slices